Washing machine to produce three-dimensional motion

ABSTRACT

A washing machine includes a main body defining an outer appearance, a tub disposed within the main body, a main drum rotatably mounted in the tub, a sub drum mounted in the main drum to be relatively rotatable with respect to the main drum, an outer shaft for rotating the main drum, an inner shaft for rotating the sub drum, being disposed inside the outer shaft, and a driving motor having a stator, an outer rotor connected to the inner shaft that is rotatable outside the stator, and an inner rotor connected to the outer shaft that is rotatable inside the stator, wherein the driving motor independently drives the main drum and the sub drum.

TECHNICAL FIELD

This specification relates to a washing machine with a structure ofimproving washing efficiency by allowing three-dimensional (3D) motionof the laundry such that the laundry can be moved in bothcircumferential and axial directions within drums, a drum assemblingmethod for the washing machine and an operation controlling methodthereof.

BACKGROUND OF THE DISCLOSURE

In general, a washing machine forcibly spins the laundry within a drumby using a mechanical force, such as a frictional force generatedbetween the drum, which is rotated by a driving force transferred from adriving motor, and the laundry, after filling detergent, washing waterand the laundry in the drum. Accordingly, the laundry can be washed by aphysical reaction such as friction or impact. Also, the laundry whichcontacts the detergent can be washed by a chemical reaction with thedetergent. The spinning of the laundry within the drum may facilitatethe chemical reaction of the detergent.

A drum type washing machine, which has been widely used in recent time,has a rotation shaft of the drum formed in a horizontal direction. Therotation shaft of the drum is alternatively inclined with respect to thehorizontal direction by a predetermined angle. The drum type washingmachine having the horizontal rotation shaft allows the laundry to bespin along an inner circumferential surface of the drum in acircumferential direction.

The laundry is rotated along the inner circumferential surface of thedrum by a centrifugal force responsive to the rotation of the drum andthe friction against the inner circumferential surface of the drum. Forassisting the spinning of the laundry, lifters are often provided on theinner circumferential surface of the drum. Here, the laundry alsoperforms a circular motion along the inner circumferential surfaceaccording to rotation speed of the drum and a falling motion from anupper side of the drum by the force of gravity. The falling motionbecomes a factor which greatly affects a washing effect.

The motion of the laundry within the drum greatly affects the washingeffect. In detail, various types of motions of the laundry may changecontact surfaces of the laundry, which rubs against the innercircumferential surface of the drum, resulting in an even washing of thelaundry, and also allowing for an increase in a physical force appliedto the laundry so as to enhance the washing effect.

Meanwhile, the washing machine is configured to run the rotation shaftby a driving motor, which has a rotor structure by use of permanentmagnets. The permanent magnet motor typically includes a stator and arotor. The stator is fixedly wound on the outside of the rotor. Therotor is in a circular shape, and has a plurality of permanent magnetsregularly aligned in an annular form. Rotor teeth may be interposedbetween the adjacent permanent magnets so as to secure permanentmagnets. Also, the rotor teeth form magnetic fluxes with the stator soas for the rotor to have a rotational force.

For the related art drum type washing machine, a single drum is rotatedto make the laundry moved. Accordingly, the laundry is merely circulatedfrom an initial position in the circumferential direction of the drumalong the inner circumferential surface of the drum (i.e., merelygenerating a circumferential-direction motion), without complicatedmotions such as an axial-direction motion and a rotation motion. Thatis, the laundry generates the two-dimensional motion because there is noroom for a separate external force applied to generate such complicatedmotions of the laundry. Consequently, the laundry is limitedly moved,which gives rise to a limited washing effect, and an increase in washingtime and power consumption.

Furthermore, the related art washing machine causes a problem in thatthose clothes are stuck on the inner circumferential surface of thedrum, with getting entangled together, after completion of washing anddehydration. Since the dehydration is performed using a centrifugalforce by the rotation of the drum, the laundry in the entangled ortwisted state is stuck on the inner circumferential surface of the drum.Hence, the laundry remains entangled until taken out of the washingmachine for drying, thereby causing wrinkles on the laundry anddifficulty in taking the laundry out of the washing machine.

SUMMARY OF THE DISCLOSURE

In general, one innovative aspect of the subject matter described herecan be implemented as a washing machine that includes a main bodydefining an outer appearance. A tub is disposed within the main body. Amain drum is rotatably mounted in the tub. A sub drum is mounted in themain drum to be relatively rotatable with respect to the main drum. Ahollow outer shaft is connected to the sub drum upon insertion into theouter shaft. The washing machine includes a driving motor having astator, an outer rotor connected to the inner shaft that is rotatableoutside the stator, and an inner rotor connected to the outer shaft thatis rotatable inside the stator. The driving motor independently drivesthe main drum and the sub drum.

This, and other aspects, can include one or more of the followingfeatures. The driving motor can drive the inner rotor and the outerrotor independently. The main drum and the sub drum can be drivenindependent of each other. An independent drive between the outer rotorand the inner rotor can induce rotations of laundry by a difference inrotation speed between the drums. The main drums and the sub drum canmove the laundry in a direction by virtue of relative rotationstherebetween, allowing the laundry to perform three-dimensional motionswhile rotating within the drums. An inner circumferential surface of themain drum can be divided into a first surface that does not face theouter circumferential surface of the sub drum and a second surface thatfaces the outer circumferential surface of the sub drum. The laundry canbe moved in the axial direction by relative motions between the firstsurface of the inner circumferential surface of the main drum and theinner circumferential surface of the sub drum.

The washing machine can include multiple main drum lifters protrudingfrom the inner circumferential surface of the main drum toward theinside in a radial direction, and multiple sub drum lifters protrudingfrom an inner circumferential surface of a sub drum toward the inside ina radial direction. The multiple main drum lifters can be provided onthe first surface. A length ratio of the main drum lifter and the subdrum lifter in an axial direction can be proportional to a length of thefirst surface of the inner circumferential surface of the main drum anda length of the inner circumferential surface of the sub drum. The maindrum lifters and the sub drum lifters can have a predetermined anglefrom an axial direction. The main drum lifters or the sub drum lifterscan be formed to have a straight inclination or a curve inclinationalong an axial direction.

The washing machine can include a main drum spider to connect the maindrum to the outer shaft, and a sub drum spider to connect the sub drumto the inner shaft. Separate spiders can be employed for the respectivedrums. The main drum and the sub drum can be independently driven by thedriving motor. The sub drum spider can include a shaft coupling portioncoupled to the inner shaft, and multiple drum fixing portions radiallyextending from the shaft coupling portion. Ends of the drum fixingportions can be fixable onto the sub drum back. The main drum spider caninclude a shaft coupling portion coupled to the outer shaft, a spidersupporting portion radially extending from the shaft coupling portion,and a drum fixing portion disposed at an end of the spider supportingportion. The drum fixing portion can be fixed onto the main drum. Thesub drum spider is rotatable independent of the main drum spider.

The main drum can have openings at front and rear sides. The sub drumcan have a sub drum back to form its rear surface. The sub drum has afront side open and the rear side closed by the sub drum back. The maindrum and the sub drum respectively can include a main drum back and asub drum back defining rear surfaces thereof. The main drum and the subdrum can have the front side open and the rear side closed by the maindrum back and the sub drum back, respectively. An outer circumferentialsurface of the sub drum can face the inner circumferential surface ofthe main drum. Only a part of the inner circumferential surface of themain drum can face the outer circumferential surface of the sub drum.The sub drum can be shorter than the main drum in length in an axialdirection, such that laundry can contact an interface between the subdrum and the main drum. A ratio (D2/D1) of a length D2 of the innercircumferential surface of the sub drum in an axial direction withrespect to a length D1 of the inner circumferential surface of the maindrum in an axial direction can be 0˜0.5, and the length D2 of the innercircumferential surface of the sub drum in the axial direction withrespect to the length D1 of the inner circumferential surface of themain drum in the axial direction can be ⅓. The washing machine canfurther include a drum guide provided along the inner circumferentialsurface of the main drum to shield an interval from the outercircumferential surface of the sub drum. The drum guide can include abody portion protruding into the main drum and coupled to the innersurface of the main drum. A guide portion can extend from the bodyportion toward the inner circumferential surface of the sub drum.

The sub drum can include a bead protruding into the sub drum along acircumferential surface while being spaced apart from an end portion ofthe sub drum by a predetermined interval. The guide portion of the drumguide can extend up to the bead of the sub drum. The end portion of thesub drum can be curled outwardly along the circumferential surface. Areinforcing bead to prevent torsion of the sub drum can be provided atthe inner circumferential surface or the outer circumferential surfaceof the sub drum. The main drum can be divided into a first portion and asecond portion having different inner diameters from each other. Theinner diameter of the first portion can be the same as the innerdiameter of the sub drum. The inner diameter of the second portion canbe greater than an outer diameter of the sub drum, thereby shielding theinterface between the main drum and the sub drum.

A rotation shaft of the washing machine may be inclined with respect toa horizontal direction by a predetermined angle. Multiple lifters can beprovided on at least one inner circumferential surface of the main drumand the sub drum to guide motions of the laundry. The sub drum can havea cylindrical portion and a drum back which can be integrally formedwith each other as one member. The receiving portion can includecoupling openings for coupling of the sub drum spider, which can includecoupling openings corresponding to the coupling openings of thereceiving portion. The sub drum can include a cylindrical portion and adrum back as independent members. The drum back can be coupled to anouter circumference of the rear of the cylindrical portion to close therear side. The receiving portion of the drum back is extendable up tothe outer circumference of the drum back. Coupling openings can beformed at a rear end portion of the cylindrical portion. An outercircumference of the drum back can be bent in a lengthwise direction ofthe drum. Coupling openings can be formed at the bent portion. The subdrum can be assembled by coupling a cylindrical portion forming an outercircumferential portion of the sub drum to a drum back disposed on arear surface of the sub drum and coupled with a sub drum spider,receiving the sub drum spider in a spider receiving portion recessedtoward the front of the drum back, and coupling arm end portions of thesub drum spider using bolts through coupling openings formed at the rearend portion of the cylindrical portion of the sub drum and a bent outercircumference of the drum back.

Another innovative aspect of the subject matter described here can beimplemented as a drum assembling method for a washing machine thatincludes a main drum and a sub drum disposed within a tub fixed to amain body and driven independent of each other, and a driving motorhaving a stator, an outer rotor and an inner rotor to independentlydrive the main drum and the sub drum. A shaft for transferring a drivingforce from the driving motor to the main and sub drums is coupled to aspider to fabricate a shaft-spider assembly. The shaft-spider assemblyis coupled to the rear of the sub drum. The sub drum is coupled to themain drum. The shaft-spider assembly is to the rear of the main drum

This, and other aspects can include one or more of the followingfeatures. In the fabricating of the shaft-spider assembly, after a maindrum spider is coupled to an outer shaft to transfer a driving forcefrom the inner rotor to the main drum, and a sub drum spider is coupledto an inner shaft to transfer a driving force from the outer rotor tothe sub drum, the inner shaft can be coupled into the outer shaft. Theinner shaft can be coupled into the outer shaft. a bearing can then bepress-fitted, after which, a waterproof seal can be inserted. Uponmounting a drum guide for sealing, the drum guide can be mounted insidethe main drum prior to inserting the sub drum into the main drum. In thecoupling of the shaft-spider assembly to the rear of the main drum, theend of the main drum spider can be coupled to the main drum.

Therefore, an aspect of the detailed description is to provide a washingmachine with a structure capable of being affected by an external forceso as to allow for various motions of the laundry, which is limitedlymoved within a drum of the washing machine.

Another aspect of the detailed description is to provide a washingmachine with a structure allowing the laundry to movethree-dimensionally by employing two drums and a driving motor forindependently driving the two drums.

Another aspect of the detailed description is to provide a drumassembling method for the washing machine with the unique structureallowing the three-dimensional (3D) motion of the laundry, and a washingmachine with a structure enabling an efficient 3D motion of the laundryand efficiently improving a washing performance.

Another aspect of the detailed description is to provide a washingmachine, which has a structure of preventing damage of the laundry,which may be caused due to use of two drums, and allows the laundry tosmoothly move by virtue of low resistance with respect to the motions ofthe laundry even though the two drums are used.

Another aspect of the detailed description is to provide a rotorstructure for a permanent magnet motor in a washing machine, capable ofreducing the occurrence of inferiority due to transformation of aprotrusion fixing end by removing the protrusion fixing end formed at aninner side toward the center from the rotor teeth, and preventing theleakage of a magnetic flux to the upper side by virtue of the reductionof the protrusion fixing end.

Another aspect of the detailed description is to provide a method forfabricating a dual motor stator in a dual drum washing machine,configured such that an inner rotor of a high torque is provided in amain drum and an outer rotor of a low torque is provided in a sub drum,by designing torque of the inner rotor side to be greater than torque ofthe outer rotor side in a manner that the number of windings of coilincreases on inner teeth by making a length of the inner teeth longerthan a length of outer teeth, and a washing machine using the same.

Another aspect of the detailed description is to provide a washingmachine capable of maximizing torque efficiency within a preset size byoptimizing a ratio of an outer diameter of a rotor with respect to anouter diameter of a stator of a permanent magnet motor, and capable ofmaximizing efficiency of the permanent magnet motor by enhancingcharacteristics of vibration and noise by minimizing cogging torque andtorque ripple under control of a height of a teeth extension portion ofrotor teeth, a distance between neighboring teeth extension portions, anarc angle of the rotor teeth, and an angle of a linear part of the teethextension portion.

Another aspect of the detailed description is to provide a method forfabricating a dual motor stator capable of minimizing redundant partsafter punching and accordingly reducing waste of components, by punchingseparately fabricated inner stator and outer stator without beingintegral with each other, and a washing machine employing the same.

Another aspect of the detailed description is to provide a washingmachine having an efficient structure to drive two drums by a singledriving motor, and not having size increase, and a driving motor for thewashing machine.

Another aspect of the detailed description is to provide a method forfabricating a washing machine including a driving motor having anoptimized number of windings on a stator for driving two drums by asingle driving motor.

Another aspect of the detailed description is to provide a washingmachine having an efficient structure to drive two drums by a singledriving motor, of reducing the number of components so as to reduce thesize of the driving motor, of shortening an operation time, and ofreducing the fabrication costs, a driving motor of the washing machine,and a method for fabricating a stator of the driving motor of thewashing machine.

Another aspect of the detailed description is to provide a washingmachine capable of effectively performing radiation by conduction andconvection by way of forming bent portions including protruding portionand concaved portion at a body of a bearing housing, in order to radiateheat generated from coil on the inner teeth (winding portions) of thestator, in the aspect of an assembled structure of the bearing housingand the stator of the driving motor in the washing machine.

Another aspect of the detailed description is to provide a structure ofa current connector and a hall sensor for a dual motor, capable ofimplementing a simplified structure, preventing an erroneous assembling,securing a space and enhancing convenience, by combining separatelyinstalled current connector and hall sensor into one integrated member,different from the structure of the conventional dual motor in which thecurrent connector and the hall sensor are separately installed at theinner stator and the outer stator, and a washing machine employing thesame.

Another aspect of the detailed description is to provide a shaftstructure for a dual drum washing machine capable of providing asimplified structure to prevent separation due to abnormal noise andvibration, which may be generated in a connection structure between aninner rotor and an outer shaft of a dual motor applied to the dual drumwashing machine, and accordingly reducing a material cost, and a washingmachine employing the same.

Another aspect of the detailed description is to provide a shaftstructure of a dual drum washing machine capable of reducing materialcost, and capable of having a simplified structure for prevention ofentangled state releasing, the entangled state releasing occurring dueto abnormal noise and vibrations generated in a connection structure ofan inner rotor and an outer shaft of a dual motor applied to a dual drumwashing machine, and a washing machine having the same.

Another aspect of the detailed description is to facilitate an assemblyprocess by fixing coupling positions of a bearing housing and a stator,by forming a fitting protrusion at a stator coupling opening formed atthe bearing housing and a fitting recess at a housing coupling openingformed at the stator, in order to improve the process of assembling thestator having outer teeth and inner teeth with the bearing housing, in adual motor including an inner rotor and an outer rotor and employed in adual drum washing machine.

Another aspect of the detailed description is to perform a function ofan inner rotor assembly guide by employing an assembly auxiliary jig forimprovement of assembly without coupling an inner rotor to a bearinghousing side.

Another aspect of the detailed description is to provide an operationand control method for a washing machine capable of reducing wrinkles oflaundry after completion of dehydration by allowing 3D motions of thelaundry by virtue of a driving motor capable of driving two drumsindependent of each other.

Another aspect of the detailed description is to provide a controlmethod for a washing machine capable of making laundry simply drawn outof a washing machine in an automatic manner after the operation of thewashing machine is completely ended.

Another aspect of the detailed description is to provide a washingmachine allowing for 3D motions by initially operating a driving motorwith preventing a starting failure due to over-current, which may begenerated upon starting the driving motor, and minimizing an amount ofheat, and simultaneously appropriately controlling a rotation directionor revolutions per minute (RPM) of the motor according to a laundryamount, temperature and the like.

Another aspect of the detailed description is to provide a washingmachine capable of precisely detecting a laundry amount, the washingmachine having two drums and a single driving motor for independentlydriving the two drums, and a laundry amount detecting method thereof.

To achieve these and other advantages and in accordance with the purposeof this specification, as embodied and broadly described herein, awashing machine including a main body defining an outer appearance, atub disposed within the main body, a main drum rotatably mounted in thetub, a sub drum mounted in the main drum to be relatively rotatable withrespect to the main drum, a hollow outer shaft connected to the maindrum, an inner shaft connected to the sub drum upon insertion into theouter shaft, and a driving motor having a stator, an outer rotorconnected to the inner shaft and rotatable outside the stator, and aninner rotor connected to the outer shaft and rotatable inside thestator, wherein the driving motor independently drives the main drum andthe sub drum.

With the configuration, the main drum and the sub drum can be driven,independent of each other, by the driving motor, so as to inducerotations of laundry by a difference in rotation speed between thedrums, thereby allowing the laundry to perform three-dimensional motionswith rotating within the drums.

The washing machine may further include a main drum spider to connectthe main drum to the outer shaft, and a sub drum spider to connect thesub drum to the inner shaft.

With the configuration, the separate spiders may be employed for therespective drums, and accordingly the drums can be independently drivenby the driving motor.

The main drum may have openings at front and rear sides. The sub drummay have a sub drum back to form its rear surface. The sub drum may havea front side open and the rear side closed by the sub drum back.

The sub drum spider may include a shaft coupling portion coupled to theinner shaft, and a plurality of drum fixing portions radially extendingfrom the shaft coupling portion. Ends of the drum fixing portions may befixed onto the sub drum back.

The sub drum back may further include a receiving portion recessedinwardly in correspondence with the sub drum spider. The sub drum spidermay be received in the receiving portion to be closely adhered onto thesub drum back.

The main drum spider may be fixed onto the main drum.

The main drum spider may include a shaft coupling portion coupled to theouter shaft, a spider supporting portion radially extending from theshaft coupling portion, and a drum fixing portion disposed at an end ofthe spider supporting portion. The drum fixing portion may be fixed ontothe main drum.

The spider supporting portion may be provided with a plurality ofcantilevers radially extending from the shaft coupling portion.Alternatively, the spider supporting portion may be in a disk shapeextending from the shaft coupling portion.

The drum fixing portion may have a ring shape to connect ends of thespider supporting portion.

The main drum spider may be coupled to an outer circumferential surfaceof the main drum. Alternatively, the main drum may include a bentportion bent from a rear end portion toward a central portion, and themain drum spider may be coupled to the bent portion.

The sub drum spider may be rotatable independent of the main drumspider.

The sub drum spider may be provided between the sub drum back and themain drum spider, to be rotated integral with the sub drum back andindependent of the main drum spider.

As an exemplary variation of the one exemplary embodiment, the main drumand the sub drum may respectively include a main drum back and a subdrum back defining rear surfaces thereof. The main drum and the sub drummay have the front side open and the rear side closed by the main drumback and the sub drum back, respectively.

With this structure, the main drum spider may be fixed onto the maindrum back.

The sub drum spider may be provided between the sub drum back and themain drum back, to be rotatable integrally with the sub drum back andindependently of the main drum back.

Meanwhile, the outer circumferential surface of the sub drum may face apart of an inner circumferential surface of the main drum.

With the configuration, the sub drum may be shorter than the main drumin length in an axial direction, such that laundry can contact aninterface between the sub drum and the main drum. Consequently, a motionthat the laundry is rotated by the difference in rotation speed betweenthe drums can be generated, thereby enabling three-dimensional motionsof the laundry.

A drum guide to seal an interval from an outer circumferential surfacemay be disposed at the inner circumferential surface of the main drum,thereby preventing laundry from being jammed between the drums.

Also, a reinforcing bead to prevent torsion of the sub drum may beprovided at the inner circumferential surface or the outercircumferential surface of the sub drum.

A rotation shaft of the washing machine may be inclined with respect toa horizontal direction by a predetermined angle.

In accordance with one exemplary embodiment, a drum assembling methodfor a washing machine may be applied to a washing machine including amain drum and a sub drum disposed within a tub fixed to a main body anddriven independent of each other, and a driving motor having a stator,an outer rotor and an inner rotor to independently drive the main drumand the sub drum, and the method may include coupling a shaft fortransferring a driving force from the driving motor to the main and subdrums to a spider to fabricate a shaft-spider assembly, coupling theshaft-spider assembly to the rear of the sub drum, coupling the sub drumto the main drum, and coupling the shaft-spider assembly to the rear ofthe main drum.

In the fabricating of the shaft-spider assembly, after a main drumspider is coupled to an outer shaft to transfer a driving force from theinner rotor to the main drum, and a sub drum spider is coupled to aninner shaft to transfer a driving force from the outer rotor to the subdrum, the inner shaft may be coupled into the outer shaft.

Here, the inner shaft may be coupled into the outer shaft, and then abearing may be press-fitted. Also, after the bearing is press-fitted, awaterproof seal may be inserted.

In the coupling of the shaft-spider assembly to the rear of the subdrum, the sub drum spider may be attached onto the rear surface of thesub drum.

In the coupling of the sub drum to the main drum, the sub drum may beinserted into the main drum.

Here, upon mounting a drum guide for sealing, the drum guide may bemounted inside the main drum prior to inserting the sub drum into themain drum.

In the coupling of the shaft-spider assembly to the rear of the maindrum, the end of the main drum spider may be coupled to the main drum.

With the configuration, a washing machine with a structure using twodrums and a hollow shaft and a dual rotor (inner rotor and outer rotor)for driving the drums independent of each other may be produced.

In accordance with another exemplary embodiment of the presentdisclosure, an inner circumferential surface of the main drum and aninner circumferential surface of the sub drum may have different lengthsfrom each other in an axial direction.

That is, an outer circumferential surface of the sub drum may face theinner circumferential surface of the main drum, more particularly, onlya part of the inner circumferential surface of the main drum may facethe outer circumferential surface of the sub drum.

Here, the sub drum may be mounted in the main drum to extend from oneend portion of the main drum in an axial direction.

A ratio (D2/D1) of a length D2 of the inner circumferential surface ofthe sub drum in an axial direction with respect to a length D1 of theinner circumferential surface of the main drum in an axial direction maybe 0˜0.5.

More preferably, the length D2 of the inner circumferential surface ofthe sub drum in the axial direction with respect to the length D1 of theinner circumferential surface of the main drum in the axial directionmay be ⅓.

To describe this in a different manner, the inner circumferentialsurface of the main drum may be divided into a first surface that doesnot face the outer circumferential surface of the sub drum and a secondsurface that faces the outer circumferential surface of the sub drum,and the ratio D2/d1 of the length D2 of the inner circumferentialsurface of the sub drum in the axial direction with respect to a lengthd1 of the first surface in an axial direction may be 0.5. The main drumand the sub drum may move the laundry in a direction by virtue ofrelative rotations therebetween.

More particularly, the inner circumferential surface of the main drummay be divided into a first surface that does not face the outercircumferential surface of the sub drum and a second surface that facesthe outer circumferential surface of the sub drum, and the laundry maybe moved in the axial direction by relative motions between the firstsurface of the inner circumferential surface of the main drum and theinner circumferential surface of the sub drum.

From the perspective of laundry, the laundry may be moved in acircumferential direction in response to the rotation of the main drumor the sub drum, and moved in the axial direction by the relativemotions between the main drum and the sub drum. Here, the motions of thelaundry in the axial direction may be allowed by the rotation of thelaundry in response to the relative motions between the main drum andthe sub drum.

In the meantime, the driving motor may independently drive the outerrotor and the inner rotor, so as to independently drive the main drumand the sub drum.

The independent driving of the outer rotor and the inner rotor may allowfor the relative rotations between the main drum and the sub drum.

With the configuration, the sub drum may be shorter than the main drumin length in an axial direction such that laundry can contact aninterface between the sub drum and the main drum. Accordingly, thelaundry can be rotated by the difference in rotation speed between thedrums, thereby performing three-dimensional motions.

Also, the driving motor may independently drive the main drum and thesub drum to cause the rotations of the laundry by the difference inrelative rotation speed between the drums, accordingly, the laundry mayperform the three-dimensional motions with rotating within the drums.Also, a structure capable of generating the optimal three-dimensionalmotion of the laundry may be provided in consideration of torquedistribution due to driving of the two drums, a mechanical force appliedto the laundry and overall movements of the laundry.

Meanwhile, a plurality of lifters may be provided on at least one innercircumferential surface of the main drum and the sub drum, thus to guidemotions of the laundry.

In accordance with another exemplary embodiment, the sub drum may have acylindrical portion and a drum back which are integrally formed witheach other as one member.

The receiving portion may have coupling openings for coupling of the subdrum spider. The sub drum spider may have coupling openingscorresponding to the coupling openings of the receiving portion. Also,the receiving portion may be formed within the sub drum back, and acantilever length of the sub drum spider may be shorter than a radius ofthe sub drum back so as to be inserted into the receiving portion.

In accordance with another exemplary embodiment, the sub drum may have acylindrical portion and a drum back as independent members, and the drumback may be coupled to an outer circumference of the rear of thecylindrical portion to close the rear side.

Also, the receiving portion of the drum back may extend up to the outercircumference of the drum back, and coupling openings may be formed at arear end portion of the cylindrical portion. An outer circumference ofthe drum back may be bent in a lengthwise direction of the drum, andcoupling openings may be formed at the bent portion.

The sub drum spider may have arms whose length is the same as the radiusof the sub drum back, and an end portion of the arm of the sub drumspider may be coupled to the rear circumference of the cylindricalportion.

In accordance with another exemplary embodiment, a method for assemblinga sub drum of a washing machine may include coupling a cylindricalportion forming an outer circumferential portion of the sub drum to adrum back, which is disposed on a rear surface of the sub drum andcoupled with a sub drum spider, receiving the sub drum spider in aspider receiving portion recessed toward the front of the drum back, andcoupling arm end portions of the sub drum spider by use of bolts throughcoupling openings formed at the rear end portion of the cylindricalportion of the sub drum and a bent outer circumference of the drum back.

In accordance with another exemplary embodiment of the presentdisclosure, the washing machine may further include a drum guideprovided along the inner circumferential surface of the main drum toshield an interval from the outer circumferential surface of the subdrum.

The drum guide may include a body portion protruding into the main drumand coupled to the inner surface of the main drum, and a guide portionextending from the body portion toward the inner circumferential surfaceof the sub drum.

The sub drum may include a bead protruding into the sub drum along thecircumferential surface with being spaced apart from an end portion ofthe sub drum by a predetermined interval. The guide portion of the drumguide may extend up to the bead of the sub drum.

With the configuration, the driving motor may independently drive themain drum and the sub drum to cause the rotations of the laundry by thedifference in relative rotation speed between the drums, accordingly,the laundry may perform the three-dimensional motions with rotatingwithin the drums. Also, the drum guide may prevent the laundry frombeing jammed into the interface where the independently driven main drumand sub drum perform the relative rotations.

As another exemplary embodiment of the present disclosure, the sub drummay include a bead protruding to the outside thereof along thecircumferential surface with being spaced apart from an end portionthereof by a predetermined interval. The guide portion of the drum guidemay extend up to the end portion of the sub drum.

Accordingly, the drum guide may prevent the laundry from being jammedinto the interface where the independently driven main drum and sub drumperform the relative rotations.

The end portion of the sub drum may be curled outwardly along thecircumferential surface. The structure may be in order to prevent thelaundry from being jammed due to the end portion of the sub drum by wayof processing the end portion of the sub drum to have a curved surface.

In accordance with another exemplary embodiment of the presentdisclosure, the main drum may be divided into a first portion and asecond portion having different inner diameters from each other. Theinner diameter of the first portion may be the same as the innerdiameter of the sub drum, and the inner diameter of the second portionmay be greater than an outer diameter of the sub drum, thereby shieldingthe interface between the main drum and the sub drum.

With the configuration, a part of the main drum may extend such that theinner circumferential surfaces of the main drum and the sub drum canhave the same radius, thereby preventing the laundry from being jammedinto the interface between the main drum and the sub drum. The structureof preventing the laundry from being jammed may be produced duringformation of the drums without use of a separate guide or the like.

Here, the end portion of the sub drum may also be curled outwardly alongthe circumferential surface, and located inside the second portion.

In accordance with another exemplary embodiment of the presentdisclosure, the main drum may further include a drum guide unitprotruding inwardly along the inner circumferential surface of the maindrum. An inner circumferential surface of the drum guide unit may beflush with the inner circumferential surface of the sub drum, therebyshielding the interface between the main drum and the sub drum.

With the configuration, the part of the main drum may protrude such thatthe inner circumferential surfaces of the main drum and the sub drum canhave the same radius at the interface therebetween. Accordingly, thelaundry may be prevented from being jammed into the interface. Thestructure of preventing the laundry from being jammed may be producedduring formation of the drums without use of a separate guide or thelike.

Here, the end portion of the sub drum may also be curled outwardly alongthe circumferential surface, and located outside more than the innercircumferential surface of the drum guide unit.

In accordance with another exemplary embodiment of the detaileddescription, a washing machine may include a plurality of main drumlifters protruding from an inner circumferential surface of a main drumtoward the inside in a radial direction, and a plurality of sub drumlifters protruding from an inner circumferential surface of a sub drumtoward the inside in a radial direction.

In more detail, the inner circumferential surface of the main drum maybe divided into a first face not facing an outer circumferential surfaceof the sub drum, and a second surface facing the outer circumferentialsurface of the sub drum. The main drum lifters may be provided on thefirst surface.

With the configuration, the driving motor may independently drive themain drum and the sub drum to cause the rotations of laundry by thedifference in relative rotation speed between the drums, accordingly,the laundry may perform the three-dimensional motions with rotatingwithin the drums. Also, the plurality of lifters may be provided on theinner circumferential surfaces of the drums such that the laundry canperform the three-dimensional motions more smoothly within the drums.

A length ratio of the main drum lifter and the sub drum lifter in anaxial direction may be proportional to a length of the first surface ofthe inner circumferential surface of the main drum and a length of theinner circumferential surface of the sub drum. This may provide thelifters in correspondence with the main drum and the sum drum having therelatively different lengths in the axial direction.

The main drum lifters and the sub drum lifters may be provided withinthe drums in parallel in an axial direction. However, the presentdisclosure may not be limited to the structure. Alternatively, the maindrum lifters and the sub drum lifters may have a predetermined anglefrom an axial direction. Here, a rotation direction of the main drum maybe determined according to an angle direction of the main drum lifterwith respect to the axial direction, and a rotation direction of the subdrum may be determined according to an angle direction of the sub drumlifter with respect to the axial direction. That is, the rotationdirection of the drum may be determined based on an inclined directionof the lifters so that laundry inside the drum may smoothly perform 3Dmotions by the lifters.

Meanwhile, sectional heights in a radial direction of the main drumlifters may become lower toward a rear side along an axial direction,and sectional heights in a radial direction of the sub drum lifters maybecome lower toward a front side along an axial direction. Accordingly,the lifters may have inclinations with respect to the axial direction toallow the laundry in the drums to efficiently move in an axialdirection, thereby allowing three-dimensional motions of the laundry.

Here, the main drum lifters or the sub drum lifters may be formed tohave a straight inclination or a curve inclination along an axialdirection.

The main drum lifters may extend from a front end portion to a rear sideof the main drum. Also, the sub drum lifter may extend from a rear endportion to a front side of the sub drum. Also, the main drum lifters andthe sub drum lifter may have inclinations becoming lower in a directionthat they face each other. This may be in order to prevent laundry to beconcentratively disposed at an inner side or an outer side of the drumdue to its motions in an axial direction, and in order to allow thelaundry to be positioned at the center of the drum for three-dimensionalmotions of the laundry.

The main drum and the sub drum may be driven independent of each otherby the driving motor. Also, the main drum and the sub drum may rotatethe laundry by relative rotations therebetween to move in an axialdirection.

The laundry may move in a circumferential direction in response torotation of the main drum or the sub drum, and move in an axialdirection with being rotated by the relative motions between the maindrum and the sub drum.

Here, the main drum lifters and the sub drum lifter may guide thelaundry to move in the circumferential direction. Also, facinginclinations of the main drum lifters and the sub drum lifters may guidemotions of the laundry in an axial direction.

According to another embodiment of the present disclosure, there isprovided a permanent magnet motor comprising: a stator including statorteeth and stator slots, and fixedly-installed as a coil is wound on thestator teeth; and a rotor including rotor teeth, a permanent magnet anda bushing, the rotor spaced from an inner circumference of the statorand rotating centering around a rotor shaft by a magnetic force. A ratioof an outer diameter of the rotor with respect to an outer diameter ofthe stator is in the range of 0.7˜0.8.

The rotor teeth include teeth extension portions protruding from theright and left sides of the rotor in an outer diameter direction. Theend of the teeth extension portion has a height less than 0.3 mm, and adistance (DW) between teeth extension portions of neighboring rotorteeth is in the range of 5.5 mm˜6.5 mm.

Preferably, an outer diameter end portion of the rotor teeth is formedsuch that the rotor teeth have an arc angle of 60°.

The teeth extension portion of the rotor teeth is provided with anextension linear portion on an outer circumference thereof. An anglebetween the extension linear portion, and a straight line from the endof the teeth extension portion to the core center is in the range of90°˜100°.

According to still another embodiment of the present disclosure, thereis provided a washing machine having a rotor structure of a permanentmagnet motor, the washing machine comprising: a main body which forms anouter appearance; a tub disposed within the main body; a main drumrotatably mounted in the tub; a sub drum mounted in the main drum to berelatively rotatable with respect to the main drum; a hollow outer shaftconnected to the main drum; an inner shaft connected to the sub drumupon insertion into the outer shaft; and a driving motor having an outerrotor and an inner rotor, wherein the driving motor includes: a statorfixedly-installed as a coil is wound on stator teeth; and a rotorincluding rotor teeth and a permanent magnet, spaced from an innercircumference of the stator, and rotating centering around a rotor shaftby a magnetic force, and wherein a ratio of an outer diameter of therotor with respect to an outer diameter of the stator is in the range of0.7˜0.8.

The rotor teeth include teeth extension portions protruding from theright and left sides of the rotor in an outer diameter direction. Theend of the teeth extension portion has a height less than 0.3 mm, and adistance (DW) between teeth extension portions of neighboring rotorteeth is in the range of 5.5 mm˜6.5 mm.

Preferably, the teeth extension portion of the rotor teeth is providedwith an extension linear portion on an outer circumference thereof. Anangle between the extension linear portion, and a straight line from theend of the teeth extension portion to the core center is in the range of90°˜100°.

In accordance with another exemplary embodiment of the presentdisclosure, a stator of a driving motor may include stator teeth andstator slots, and be fixedly-installed as a coil is wound on the statorteeth. The outer rotor and the inner rotor may include rotor teeth, apermanent magnet and a bushing, be spaced from an inner circumference ofthe stator, and rotate centering around a rotor shaft by a magneticforce. The rotor teeth may include a teeth extension portion extendingfrom a side end of an outer circumference of the rotor teeth in acircumferential direction, a cut recess cut in a concaved manner fromthe outer circumference of the rotor teeth toward the center of therotor shaft, and an insertion recess cut in a concaved manner in aradial direction from an inner circumference of the rotor teeth toinsert an injection-molding material of the bushing thereinto.

The insertion recess may include a first insertion recess through whichan injection-molding material of the bushing is inserted into the rotorteeth, and a second insertion recess extending from the first insertionrecess to a radial direction of the rotor shaft to integrally-fix thebushing and the rotor teeth after hardening the injection-moldingmaterial of the bushing inserted thereinto.

The second insertion recess may be formed as a through hole having atleast one of circular, oval, polygonal and triangular shapes each havinga diameter larger than a width of the first insertion recess.

The rotor teeth may further include a cut opening extending from the cuthole toward the center of the rotor shaft to form a flux barrier as aninjection-molding material of the bushing is filled therein. The cutopening which forms the flux barrier may preferably be formed in acircular or oval shape having a diameter larger than a width of the cutrecess, so as to prevent leakage of a magnetic flux of the permanentmagnet positioned between the rotor teeth.

The cut recess and the flux barrier cut opening of the rotor teeth maybe filled with an injection-molding material of the bushing. This mayprevent separation of the rotor teeth. Also, since a space between theteeth extension portion of the rotor teeth and the permanent magnet maybe filled with the injection-molding material of the bushing, the rotorteeth and the permanent magnet may be integrally fixed to each other.This may prevent separation of the rotor teeth from the rotor core dueto a centrifugal force.

An outer circumferential end of the rotor teeth may have a curvaturelarger than that of the annular rotor. This may change a spacingdistance between an outer circumferential surface of the rotor teeth andan inner circumferential surface of the stator.

In accordance with another exemplary embodiment of the presentdisclosure, the dual motor stator may include an inner stator includinga plurality of inner teeth protruding toward the center in a ring shape,an inner yoke 13 which forms a ring shape of an inner stator, and innerslots serving as spaces between the inner teeth and the inner yoke, andan outer stator including a plurality of outer teeth protruding in aradial direction in a ring shape, an outer yoke contacting an outercircumferential surface of the inner yoke and forming a ring shape ofthe outer stator, and outer slots serving as spaces between the outerteeth and the outer 230. The inner stator and the outer stator may faceeach other at an outer circumferential surface of the inner yoke and aninner circumferential surface of the inner yoke and be coupled to eachother with being spaced from each other.

Also, the stator may be configured such that a length of the inner teethmay be longer than a length of the outer teeth, by which the number ofwindings of the coil wound on the inner teeth can be larger than that ofthe coil wound on the outer teeth. Consequently, torque of the innerrotor may be larger than torque of the outer rotor, thereby making arotational force of the main drum greater than that of the sub drum.

The stator may include an insulator installed at part between an outercircumferential surface of the inner yoke and an inner circumferentialsurface of the outer yoke to shield a magnetic force. The insulator maypreferably be formed of a PBT-based plastic material.

In the method for fabricating the stator, a pair of inner stators may befabricated in a punching manner in a state that the inner teeth aredisposed to be engaged with each other in a lengthwise direction, and apair of outer stators may be fabricated in a punching manner in a statethat the outer teeth are disposed to be engaged with each other in alengthwise direction. This may minimize the amount of redundant partsafter punching in the inner stators and the outer stators, therebyminimizing the loss of components.

The inner stator extending in the lengthwise direction may beimplemented in a ring shape as one end and another end thereof areconnected to each other. And, the outer stator extending in thelengthwise direction may be wound on an outer circumference of the innerstator in a ring shape.

Another exemplary embodiment for a washing machine according to thisdisclosure may include a tub disposed inside a main body definingappearance, a main drum rotatably mounted in the tub, a sub drum mountedin the main drum to be relatively rotatable with the main drum, a hollowouter shaft connected to the main drum, an inner shaft connected to thesub drum within the outer shaft, and a driving motor having a stator, anouter rotor connected to the inner shaft and rotatable outside thestator, and an inner rotor connected to the outer shaft and rotatableinside the stator, wherein the stator may include an inner stator facingthe inner rotor and an outer stator facing the outer rotor, wherein eachof the inner stator and the outer stator of the stator may include aplurality of articulated bobbins connected into a ring shape, aplurality of teeth inserted into the articulated bobbins, respectively,and a tooth ring for connecting end portions of the plurality of teethinto a ring shape.

With the configuration, as the main drum and the sub drum areindependently worked by the driving motor, the laundry may be rotateddue to a difference of a relative rotation speed between the drums,whereby the laundry can perform a three-dimensional motion with rotatingwithin the drums.

Also, the two stators may be employed for driving the two independentrotors, and each stator may include articulated bobbins for improvementof a winding space factor, which may result in enhancement ofperformance of the driving motor and optimization of the driving motor.

In addition, the use of the tooth ring for reducing cogging torque andpreventing lowering of an output may arouse an optimal structure fordriving the two independent rotors.

Here, in accordance with one exemplary embodiment, when the teeth aresegment type teeth, each of the inner stator and the outer stator of thestator may further include an annular yoke for connecting end portionsof the plurality of articulated bobbins, such that the plurality ofarticulated bobbins can be mounted between the yoke and the tooth ring.

In accordance with another exemplary embodiment, when the teeth areintegrally formed with an articulated yoke for connecting end portionsof the teeth, the articulated yoke may be bent into a ring shape, suchthat the plurality of articulated bobbins can be mounted between theannularly-bent articulated yoke and the tooth ring.

In those exemplary embodiments, each of the plurality of articulatedbobbins may be wound with a coil.

Each articulated bobbin may include a body part having a receivingportion for insertion of the tooth therein, and articulated parts formedat both side surfaces of the body part to be bent. Accordingly, thearticulated parts of the plurality of articulated bobbins can beinterconnected to one another.

In accordance with one exemplary embodiment of this disclosure, a methodfor fabricating a stator of a driving motor for a washing machine mayinclude a bobbin connecting step of connecting a plurality ofarticulated bobbins in the form of a belt, a tooth inserting step ofinserting teeth into the plurality of connected articulated bobbins,respectively, an automatic winding step of automatically winding a coilon each tooth-inserted articulated bobbin, a yoke connecting step ofconnecting the coil-wound articulated bobbins into a ring shape, and atooth ring connecting step of connecting a tooth ring of a ring shapefor connecting end portions of the teeth.

The automatic winding step may be performed to automatically wind a coilon each of the articulated bobbins in an aligned state.

The coil may be automatically wound on the articulated bobbin in orderto improve a winding space factor, which may result in enhancement ofthe performance of the driving motor and optimization of the drivingmotor.

Here, when the teeth are segment type teeth, the yoke connecting stepmay be performed to connect the articulated bobbins to the yoke of thering shape.

Also, for integral teeth integrally formed with the articulated yoke forconnecting the end portions of the teeth, the yoke connecting step maybe performed to bend the articulated yoke into the ring shape.

One exemplary embodiment of a driving motor for a washing machineaccording to this disclosure, when those configurations are limited tothe driving motor for the washing machine, may include an inner statorhaving a ring shape, an outer stator having a ring shape and locatedoutside the inner stator, an inner rotor disposed inside the innerstator, and an outer rotor disposed outside the outer stator, whereineach of the inner stator and the outer stator may include a plurality ofarticulated bobbins connected into a ring shape, a plurality of teethinserted into the articulated bobbins, respectively, and a tooth ringfor connecting end portions of the plurality of teeth into a ring shape.

Another exemplary embodiment for a washing machine according to thisdisclosure may include a tub disposed inside a main body definingappearance, a main drum rotatably mounted in the tub, a sub drum mountedin the main drum to be relatively rotatable with the main drum, a hollowouter shaft connected to the main drum, an inner shaft connected to thesub drum within the outer shaft, and a driving motor having a stator, anouter rotor connected to the inner shaft and rotatable outside thestator, and an inner rotor connected to the outer shaft and rotatableinside the stator, wherein the stator may an inner stator facing theinner rotor and an outer stator facing the outer rotor, and the innerstator and the outer stator may be integrally formed by an insulator.

The inner stator may be formed by receiving an inner tooth core, whichincludes a plurality of inner teeth and an inner yoke, in the insulatorand winding the coil on the insulator, and the outer stator may beformed by receiving an outer tooth core, which includes a plurality ofouter teeth and an outer yoke, in the insulator and winding the coil onthe insulator.

Here, the insulator may include a flux barrier for shielding a magneticforce by spacing the inner tooth core and the outer tooth core apartfrom each other.

Also, the insulator may include an inner tooth core receiving parthaving inner tooth receiving portions for receiving the plurality ofinner teeth, and an inner yoke receiving portion for receiving the inneryoke, and an outer tooth core receiving part having outer toothreceiving portions for receiving the plurality of outer teeth, and anouter yoke receiving portion for receiving the outer yoke. The fluxbarrier may be interposed between the inner yoke receiving portion andthe outer yoke receiving portion.

Inner slots may be formed between the inner tooth receiving portions forreceiving the plurality of inner teeth, respectively, and outer slotsmay be formed between the outer tooth receiving portions for receivingthe plurality of outer teeth, respectively. A coil may be wound onoutside of each of the inner tooth receiving portions and the outertooth receiving portions.

The insulator may be formed by coupling an upper insulator and a lowerinsulator which face each other. The flux barrier may protrude from atleast one of the upper insulator and the lower insulator, thus to shielda magnetic force by spacing the inner tooth core and the outer toothcore apart from each other upon coupling of the upper insulator and thelower insulator.

The insulator may be formed of PBT-based plastic.

With the configuration, as the main drum and the sub drum areindependently worked by the driving motor, the laundry may be rotateddue to a difference of a relative rotation speed between the drums,whereby the laundry can perform a three-dimensional motion with rotatingwithin the drums.

Also, the insulator may serve even as a bobbin and accordingly thenumber of components and an entire size of the driving motor can bereduced, which may result in preventing an increase in an entire size ofthe washing machine even if two stators for driving two independentrotors are employed.

One exemplary embodiment of a driving motor for a washing machineaccording to this disclosure, when those configurations are limited tothe driving motor for the washing machine, may include an inner statorhaving a ring shape, an outer stator having a ring shape and locatedoutside the inner stator, an inner rotor disposed inside the innerstator, an outer rotor disposed outside the outer stator, and aninsulator for integrally forming the inner stator and the outer stator,wherein the inner stator may be formed by receiving an inner tooth core,which includes a plurality of inner teeth and an inner yoke, in theinsulator and winding the coil on the insulator, and the outer statormay be formed by receiving an outer tooth core, which includes aplurality of outer teeth and an outer yoke, in the insulator and windingthe coil on the insulator. Here, the insulator may include a fluxbarrier for shielding a magnetic force by spacing the inner tooth coreand the outer tooth core apart from each other.

The insulator may include an inner tooth core receiving part havinginner tooth receiving portions for receiving the plurality of innerteeth, and an inner yoke receiving portion for receiving the inner yoke,and an outer tooth core receiving part having outer tooth receivingportions for receiving the plurality of outer teeth, and an outer yokereceiving portion for receiving the outer yoke. The flux barrier may beinterposed between the inner yoke receiving portion and the outer yokereceiving portion.

The insulator may be formed by coupling an upper insulator and a lowerinsulator which face each other. The flux barrier may protrude from atleast one of the upper insulator and the lower insulator, thus to shielda magnetic force by spacing the inner tooth core and the outer toothcore apart from each other upon coupling of the upper insulator and thelower insulator.

One exemplary embodiment of a method for fabricating a stator of adriving motor for a washing machine according to this disclosure mayinclude a stator core forming step of stacking an inner tooth corehaving inner teeth and an inner yoke, and an outer tooth core havingouter teeth and an outer yoke, a stator core inserting step of insertingthe inner tooth core and the outer tooth core in one of an upperinsulator and a lower insulator, which are coupled to form an innertooth receiving part and an outer tooth receiving part and face eachother, a stator assembling step of coupling the upper insulator to thelower insulator, and a coil winding step of winding a coil on an outsideof inner tooth receiving portions for receiving the inner teeth of theinner stator receiving part, and on an outside of outer tooth receivingportions for receiving the outer teeth of the outer stator receivingpart.

In the stator core inserting step, the inner tooth core and the outertooth core may be inserted with being spaced apart from each other byinterposing therebetween a flux barrier, which is formed at at least oneof the upper insulator and the lower insulator.

With the configuration, the assembling of the stator can be performed inan easy and simple manner, and the insulator can serve as the bobbin aswell, which may allow for reduction of the entire number of componentsand an entire size of the driving motor. Therefore, even if two statorsfor driving two independent rotors are employed, an increase in anentire size of the washing machine can be avoided.

In accordance with another exemplary embodiment of the presentdisclosure, the driving motor may have a bearing housing structure forenhancement of radiation of a dual motor stator. The structure mayinclude a bearing housing assembled to a stator having outer teeth,inner teeth, a yoke and a housing coupling opening, and provided with abody, a bearing shaft hole, a housing fixing opening and a statorcoupling opening. The body of the bearing housing may include aprotruding portion at a position corresponding to the winding portion ofthe inner teeth, and a concaved portion at a position corresponding to aslot between the inner teeth.

Preferably, the concaved portion may be formed as a space for convectionof heat generated from the winding portion of the inner teeth, and theprotruding portion of the body of the bearing housing may be formed as aconducting portion for radiating heat generated from the winding portionof the inner teeth to the outside by conduction.

The protruding portion of the body of the bearing housing may be spacedfrom the coil wound on the winding portion of the inner teeth by apredetermined insulating distance.

In accordance with another exemplary embodiment of the presentdisclosure, the driving motor may have a structure of a currentconnector and a hall sensor for a dual motor. The structure may includea stator having inner teeth and outer teeth, a current connector applypower to an outer winding portion of the outer teeth and an innerwinding portion of the inner teeth in an integrated manner; and a hallsensor connector configured to apply power to an outer hall sensor andan inner hall sensor in an integrated manner.

The current connector may supply a current from a power unit to theouter winding portion and the inner winding portion in parallel, and theapplied to the outer winding portions and the inner winding portion maybe integrally connected to one ground.

The hall sensor connector may supply a current from the power unit tothe outer hall sensor and the inner hall sensor in parallel through theintegrated hall sensor connector, and hall sensing signals detected fromthe outer stator and the inner stator may be connected to the integratedhall sensor connector in parallel. The current applied from the outerhall sensor and the inner hall sensor may be connected to one ground.

The driving motor may further include an outer temperature sensor and aninner temperature sensor for detecting temperatures of the outer statorand the inner stator, respectively. The outer temperature sensor and theinner temperature sensor may contact the outer winding portion and theinner winding portion to measure temperatures.

With the configuration, a current from the power unit may be supplied tothe outer temperature sensor and the inner temperature sensor, inparallel, through the integrated hall sensor connector, and signalsdetected from the outer temperature sensor and the inner temperaturesensor may be connected to the integrated hall sensor connector inparallel. The hall sensor unit including the outer hall sensor and theinner hall sensor, and a temperature sensor unit including the outertemperature sensor and the inner temperature sensor may be connected toeach other in parallel to be integrally connected to one ground.

In accordance with another exemplary embodiment of the presentdisclosure, the washing machine may include a spring washer insertedinto a connection part of the outer shaft and the inner rotor, whichresults in attenuation of vibrations of the outer shaft to preventnoise, and prevention of separation of the outer shaft 81 due tovibrations.

A stopping ring may further be provided at a connection part of theouter shaft and the inner rotor to secure the spring washer so as toprevent separation of the spring washer in an axial direction.Preferably, the stopping ring may be implemented as a C-ring.

A stopping ring recess may be concaved from an outer circumference ofthe outer shaft toward the center. The C-ring may be inserted into thestopping ring recess, and prevent separation of the spring washer in theaxial direction.

An inner bushing may be installed between the outer shaft and the innerrotor to transfer a rotational force of the inner rotor to the outershaft. The spring washer may be installed at the connection part of theinner bushing and the outer shaft to prevent vibration and noise in theaxial direction of the outer shaft and noise.

Also, a stopping ring may further be provided at the connection part ofthe outer shaft and the inner bushing to fixe the spring washer. Thespring washer may be formed as an annular member which encompasses anouter circumference of the outer shaft on an upper surface of the innerbushing.

The spring washer may preferably be implemented as an annularconcave-convex member having a protruding portion and a concavedportion.

According to still another embodiment of the present invention, there isprovided a shaft structure for a dual drum washing machine, comprising:an outer shaft formed in a hollow type; an inner shaft inserted into theouter shaft; a driving motor having a stator, an outer rotor connectedto the inner shaft and rotating outside the stator, and an inner rotorconnected to the outer shaft and rotating inside the stator; a springwasher inserted into the outer shaft at a connection part of the outershaft and the inner rotor; and an inner rotor nut configured to forciblyfix the inner rotor after the spring washer has been insertion-coupledto the outer shaft. Under this configuration, vibrations of the outershaft in an axial direction can be attenuated to prevent noise, andentangled state releasing due to vibration can be prevented.

The shaft structure of the present invention may further comprise aplain washer insertion-coupled to part between the inner rotor and thespring washer on the outer circumference of the outer shaft.

A male screw portion is formed on the outer circumference of the outershaft, and a female screw portion is formed on the inner circumferenceof the inner rotor nut. As the male screw portion and the female screwportion are screw-coupled to each other, the spring washer can beprevented from deviating in an axial direction.

An inner bushing is installed between the outer shaft and the innerrotor, so that a rotation force of the inner rotor can be transferred tothe outer shaft.

According to another embodiment of the present invention, the springwasher is implemented in the form of an annular concave-convex memberformed on an upper surface of the inner bushing so as to cover the outercircumference of the outer shaft. This can prevent vibrations of theouter shaft in an axial direction, and noise.

The annular concave-convex member includes a protrusion part and aconcaved part.

An inner ball bearing is installed between the outer shaft and the innershaft, so that the driving motor can drive the outer shaft and the innershaft, independently.

In accordance with another exemplary embodiment of the presentdisclosure, in the assembly structure of the driving motor including abearing housing with a housing main body, a bearing shaft hole and astator coupling opening, and a stator with outer teeth, inner teeth, ayoke and a housing coupling opening, the stator coupling opening mayinclude a fitting protrusion and the housing coupling opening mayinclude a fitting recess such that the fitting protrusion can beinserted into the fitting recess, thereby enhancing an assemblycharacteristic between the bearing housing and the stator of the dualmotor.

The stator coupling opening and the housing coupling opening may beprovided with coupling openings communicated with each other when thebearing housing and the stator are assembled to each other. In a statethat the fitting protrusion has been insertion-fixed to the fittingrecess, the bearing housing and the stator may be assembled to eachother by screws through the coupling openings.

The stator coupling opening may protrude from the body of the bearinghousing by a predetermined height, and the housing coupling opening mayprotrude from the yoke of the stator by a predetermined height.

Also, the stator may include a plurality of spacers protruding from theyoke so that the stator can be coupled to the bearing housing with a gaptherebetween.

In accordance with another exemplary embodiment of the presentdisclosure, an a method for driving a washing machine may include awashing step of performing a washing process by supplying washing waterand a detergent, a rinsing step of performing a rinsing process bysupplying rinsing water, a dehydrating step of discharging rinsing waterand performing a dehydrating process, and a laundry arranging step ofseparating laundry from the main drum and the sub drum and releasing anentangled state of the laundry after the dehydration process. The methodmay further include a drying step of performing a drying process to drythe laundry, and the laundry arranging step may be performed prior tothe drying step.

The laundry arranging step may include a laundry separating process ofseparating the laundry from inner surfaces of the main drum and the subdrum in response to the relative motions between the main drum and thesub drum, and an entangled state releasing process of releasing anentangled state of the laundry while the laundry rotates by relativemotions of the main drum and the sub drum and moves in a circumferentialdirection and an axial direction. The laundry arranging step may furtherinclude a laundry automatic-drawing step of drawing the laundry to theoutside by relative motions of the main drum and the sub drum.

In accordance with another exemplary embodiment of the presentdisclosure, a method for controlling a washing machine may include alaundry separating step of driving by the driving motor the main drumand the sub drum to perform the relative motions to separate the laundryfrom the inner surfaces of the main drum and the sub drum after thedehydrating step of draining rinsing water and performing a dehydrationprocess, and an entangled state releasing step of driving by the drivingmotor the main drum and the sub drum to perform the relative motionssuch that the entangled state of the laundry can be released withrotating and moving in a circumferential direction and an axialdirection. And, the method may further include a laundryautomatic-drawing step of driving by the driving motor the main drum andthe sub drum by the driving motor to perform relative motions so thatthe laundry may be discharged to the outside of the door after the doorhas opened.

The driving motor may independently rotate the outer rotor and the innerrotor such that the main drum and the sub drum can perform the relativerotations. Preferably, the sub drum and the main drum may rotate inmutually opposite directions, or rotate at different rotation speeds inthe same rotation direction.

In accordance with another exemplary embodiment of the presentdisclosure, the method for driving the washing machine may include athree-dimensional washing process of rotating laundry and moving thelaundry in a circumferential direction and an axial direction byrelative motions of the main drum and the sub drum which performs thewashing process by supplying the washing water and the detergent.

Also, the washing step may further include a general washing process ofmoving the laundry in the circumferential direction by the rotations ofthe main drum and the sub drum.

In accordance with another exemplary embodiment of the presentdisclosure, the driving motor may drive the main drum and the sub drumto relatively rotate such that the laundry can rotate and move in thecircumferential and axial directions, or drive the main drum and the subdrum to integrally rotate each other such that the laundry can move onlyin the circumferential direction, according to a laundry amount measuredin the washing step of performing the washing process by supplying thewashing water and the detergent.

In detail, when a laundry amount is less than ⅓ of the maximum load ofthe driving motor, the driving motor may rotate the main drum and thesub drum in opposite directions. When a laundry amount is more than ⅓and less than ⅔ of the maximum load of the driving motor, the drivingmotor may rotate the main drum and the sub drum in the same directionwith different speeds. When a laundry amount is more than ⅔ of themaximum load of the driving motor, the driving motor may integrallyrotate the main drum and the sub drum in the same direction.

In accordance with another exemplary embodiment of the presentdisclosure, the washing machine may further include a control unit tocontrol operations of the outer rotor and the inner rotor, and uponinitially operating the driving motor, the control unit may operate theouter rotor and the inner rotor with starting RPM smaller than or thesame as each target RPM of the outer rotor and the inner rotor.

The control unit may control the driving motor to sequentially drive theouter and inner rotors, starting from one rotor having a large torque.

In accordance with another exemplary embodiment of the presentdisclosure, the washing machine may further include comprises a laundryamount detection unit 200 configured to detect a laundry amount. If apredetermined time lapses after the driving motor has started tooperate, the control unit may control a rotation direction or an RPM ofeach of the outer rotor and the inner rotor according to a laundryamount.

When a laundry amount is less than a reference laundry amount, thecontrol unit may rotate the main drum and the sub drum by driving theouter rotor and the inner rotor in opposite directions. When a laundryamount is more than the reference laundry amount, the control unit mayrotate the outer rotor and the inner rotor in the same direction.

When a laundry amount is less than a first reference laundry amount, thecontrol unit may rotate the outer rotor and the inner rotor in oppositedirections. When a laundry amount is more than a second referencelaundry amount greater than the first reference laundry amount, thecontrol unit may rotate the outer rotor and the inner rotor in the samedirection.

When a laundry amount is more than the first reference laundry amountand less than the second reference laundry amount, the control unit maycontrol rotation directions or RPMs of the outer rotor and the innerrotor according to a heat generation amount or torque of the drivingmotor.

In accordance with another exemplary embodiment of the presentdisclosure, the washing machine may further include a temperaturedetection unit provided at the outer rotor or the inner rotor, andconfigured to detect a temperature. When a temperature is more than areference temperature, the control unit may control the outer rotor andthe inner rotor to rotate with the same RPM.

In accordance with another exemplary embodiment of the presentdisclosure, a method for controlling a washing machine may includeinitially operating the driving motor with the same starting RPM smallerthan target RPMs of the outer rotor and the inner rotor, and operatingthe outer rotor and the inner rotor with the respective target RPMs whena predetermined time lapses after initially-operating the driving motor.

The method may include comparing torques of the outer rotor and theinner rotor, firstly initial-operating one rotor having a larger torqueand then initial-operating another rotor having a smaller torque basedon a comparison result, and operating the outer rotor and the innerrotor with respective target RPMs if a predetermined time lapses afterthe driving motor has started to operate. The method may further includedetecting a laundry amount.

The step of operating the outer rotor and the inner rotor may includeoperating the main drum and the sub drum by rotating the outer rotor andthe inner rotor in opposite directions when a laundry amount is lessthan a reference laundry amount, and rotating the outer rotor and theinner rotor in the same direction with different RPMs when a laundryamount is more than the reference laundry amount.

Also, the method for controlling the washing machine may further includedetecting a temperature of the outer rotor or the inner rotor, andcontrolling the outer rotor and the inner rotor to rotate with the sameRPM when the temperature is more than a reference temperature.

A washing machine according to an embodiment of the present inventioncomprises a main body which forms an outer appearance; a tub disposedwithin the main body; a main drum rotatably mounted in the tub, andaccommodating laundry therein; a sub drum mounted in the main drum so asto be relatively rotatable with respect to the main drum; a drivingmotor including a stator, an outer rotor connected to the sub drum androtating outside the stator, and an inner rotor connected to the maindrum and rotating inside the stator; and a control unit configured todrive the outer rotor and the inner rotor. The control unit drives theinner rotor and the outer rotor into particular RPMs, respectively, andapplies a braking command to the inner rotor and the outer rotor. Then,the control unit detects a first laundry amount inside the main drum anda second laundry amount inside the sub drum based on braking times ofthe inner and outer rotors.

In a washing machine according to another embodiment of the presentinvention, the control unit includes a master controller configured todrive the inner rotor, and to detect the first laundry amount based onthe braking time of the inner rotor; and a slave controller connected tothe master controller, configured to drive the outer rotor, and todetect the second laundry amount based on the braking time of the outerrotor.

The master controller generates a braking command for the outer rotor,and transmits the braking command to the slave controller. Then, themaster controller generates a braking command for the inner rotor aftera particular time has lapsed.

The washing machine further comprises a current detector configured todetect a first current and a second current applied to the inner rotorand the outer rotor, respectively.

According to an embodiment of the present invention, there is provided alaundry amount detecting method for a washing machine, the washingmachine comprising a main body which forms an outer appearance; a tubdisposed within the main body; a main drum rotatably mounted in the tub,and accommodating laundry therein; a sub drum mounted in the main drumso as to be relatively rotatable with respect to the main drum; and adriving motor including a stator, an outer rotor connected to the subdrum and rotating outside the stator, and an inner rotor connected tothe main drum and rotating inside the stator, the method comprising:initially driving the inner rotor and the outer rotor; braking the innerrotor and the outer rotor when the inner rotor and the outer rotor reachparticular RPMs; and detecting a first laundry amount inside the maindrum and a second laundry amount inside the sub drum based on brakingtimes of the inner rotor and the outer rotor.

The method further comprises displaying one of the first laundry amount,the second laundry amount, and a final laundry amount determined basedon the first and second laundry amounts (S160).

According to another embodiment of the present invention, there isprovided a laundry amount detecting method for a washing machine, thewashing machine comprising a main body which forms an outer appearance;a tub disposed within the main body; a main drum rotatably mounted inthe tub, and accommodating laundry therein; a sub drum mounted in themain drum so as to be relatively rotatable with respect to the maindrum; a driving motor including a stator, an outer rotor connected tothe sub drum and rotating outside the stator, and an inner rotorconnected to the main drum and rotating inside the stator; a mastercontroller configured to drive the inner rotor; and a slave controllerconfigured to drive the outer rotor, the method comprising: initiallydriving the inner rotor and the outer rotor by the master controller andthe slave controller, respectively; braking the inner rotor and theouter rotor by the master controller, when the inner rotor and the outerrotor reach particular RPMs; and detecting a first laundry amount insidethe main drum and a second laundry amount inside the sub drum by themaster controller and the slave controller, based on braking times ofthe inner rotor and the outer rotor.

The present disclosure may provide one or more of the following effectswith those configurations.

Two drums which rotate independent of each other may be employed toallow laundry within the drums to move three-dimensionally. Accordingly,the three-dimensional motions of the laundry can improve the washingperformance of a washing machine and reduce a washing time thereof.

A structure capable of generating the optimal three-dimensional motionof the laundry may be provided in consideration of torque distributiondue to driving the two drums, a mechanical force applied to the laundryand overall movements of the laundry, thus to improve the washingperformance.

The two drums which rotate independent of each other may be providedwith lifters, respectively, to render laundry move more smoothly,thereby improving the washing performance and the washing time of thewashing machine.

A protrusion fixing end formed at an inner side toward the center fromthe rotor teeth may be removed to reduce the occurrence of inferioritydue to transformation of a protrusion fixing end. Also, the leakage of amagnetic flux to the upper side may be prevented by virtue of thereduction of the protrusion fixing end. A cut recess as a cut throughhole may be formed inside the rotor teeth in an outer circumferentialdirection to be integrally coupled to a bushing by an injection-molding,thereby simplifying the assembly of the rotor integrated with a rotorcore and fixing the core by prevention of separation of the rotor due toa centrifugal force.

An inner rotor of a high torque may be provided in a main drum and anouter rotor of a low torque may be provided in a sub drum, by designingtorque of the inner rotor side to be greater than torque of the outerrotor side in a manner that the number of windings of coil increases oninner teeth by making a length of the inner teeth longer than a lengthof outer teeth.

In the present invention, a ratio between an outer diameter of the rotorand an outer diameter of the stator of the permanent magnet motor may beoptimized for a maximum torque within a preset size. This can maximizeefficiency of the permanent magnet motor.

In the present invention, cogging torque and torque ripple can beminimized under control of a height of a teeth extension portion ofrotor teeth, a distance between neighboring teeth extension portions, anarc angle of the rotor teeth, and an angle of a linear part of the teethextension portion. This can enhance characteristics of vibration andnoise, resulting in stable rotation of the motor.

In a method for fabricating a dual motor stator, redundant parts afterpunching can be minimized and accordingly waste of components can bereduced, by punching separately fabricated inner stator and outer statorwithout being integral with each other, and a washing machine employingthe same.

Also, two stators for driving two independent rotors may be employed,and an automatic coil winding in an aligned manner may be allowed by useof articulated bobbins, resulting in improvement of a winding spacefactor and performance of a driving motor, and reduction of workingtime.

A tooth ring for reducing cogging torque and preventing lowering of anoutput may be used, so as to improve the performance of the drivingmotor.

A core having an efficient teeth structure to be used for thearticulated bobbins may be provided, thereby reducing wasted pieces,which are generated upon a core fabrication.

Also, as the two stators for driving the two independent rotors may beemployed to be integrally assembled by an insulator, and the insulatormay serve as a bobbin as well, stator assembling may be carried out inan easy and simple manner, and the number of components and an entiresize of the driving motor can be reduced. Therefore, an increase in anentire size of the washing machine can be avoided even if the twostators for driving the two independent rotors are used.

In the aspect of an assembled structure of the bearing housing and thestator of the driving motor in the washing machine, bent portionsincluding protruding portion and concaved portion may be formed at abody of a bearing housing, in order to radiate heat generated from coilon the inner teeth (winding portions) of the stator capable ofeffectively performing radiation by conduction and convection.

A current connector and a hall sensor connector, which have beenprovided at an inner stator and an outer stator, respectively, can becombined into one integrated member so as to implement a simplifiedstructure, secure a space and enhancing convenience. This structure mayalso prevent an erroneous assembling, which may result in an increase inconvenience for assembly of a dual motor.

More simplified structure can be employed by improving a shaft structureof a washing machine with such dual drum and dual motor, therebyattenuating vibration between an inner rotor and an outer rotor toprevent unexpected noise and preventing separation of shafts.

In a dual motor including an inner rotor and the outer rotor, employedin a dual drum washing machine, in order to improve the process ofassembling the stator having outer teeth and inner teeth with thebearing housing, a fitting protrusion may be provided at a statorcoupling opening formed at the bearing housing and a fitting recess maybe provided at a housing coupling opening formed at the statorfacilitate an assembly process, so as to fix coupling positions of thebearing housing and the stator, thereby facilitating the assemblyprocess.

A function of an inner rotor assembly guide may be performed byemploying an assembly auxiliary jig for improvement of assembly when aninner rotor is independently coupled to the outer shaft without coupledto a bearing housing side.

Two drums and a driving motor which can independently drive the twodrums may be driven and controlled to allow for three-dimensionalmotions of laundry, accordingly, the laundry can be easily separatedfrom inner circumferential surfaces of the drums after dehydration andeasily released from an entangled state, thereby reducing wrinkles onthe laundry.

The laundry can be easily drawn out of the washing machine in anautomatic manner after the operation of the washing machine is ended,thereby improving user's convenience.

The laundry can be controlled to perform the three-dimensional motionsor typical two-dimensional motions according to a laundry amount, so asto prevent an overload of the driving motor and achieve an optimalwashing performance, thereby improving washing efficiency.

The laundry may be controlled to perform three-dimensional motions inconsideration of torque distribution due to driving of two drums, amechanical force applied to the laundry and overall movements of thelaundry.

Two rotors of a dual motor may be controlled to have the same RPM ordifferent starting time so as to prevent a starting failure due toover-current, which may be generated upon starting the driving motor,and maintain a minimum amount of heat, thereby improving systemstability.

Also, the rotation direction or RPM of the driving motor can beappropriately controlled according to loads such as a laundry amount,temperature and the like so as to allow for three-dimensional motions ofthe laundry, resulting in improvement of a washing performance.

In the washing machine having two drums and a single driving motor forindependently driving the two drums, a laundry amount is detected withrespect to each drum. This can result in precise detection of thelaundry amount.

In the present invention, the laundry amounts inside the two drums aredetected in different manners. This can allow the laundry amounts to bemore precisely detected, and can reduce the amount of washing water andelectricity required to perform washing, rinsing and dehydratingprocesses.

Further scope of applicability of the present application will becomemore apparent from the detailed description given hereinafter. However,it should be understood that the detailed description and specificexamples, while indicating preferred embodiments of the disclosure, aregiven by way of illustration only, since various changes andmodifications within the spirit and scope of the disclosure will becomeapparent to those skilled in the art from the detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the disclosure and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments andtogether with the description serve to explain the principles of thedisclosure.

In the drawings:

FIG. 1 is a schematic view of a washing machine according to anembodiment of the present invention;

FIG. 2 is a disassembled perspective view of a main drum and a sub drum;

FIG. 3 is a coupled view of the main drum and the sub drum of FIG. 2;

FIG. 4 is a disassembled perspective view of a driving motor;

FIG. 5 is a schematic view showing a connected state of the drivingmotor, the main drum and the sub drum;

FIG. 6 is an enlarged view showing a reinforcing bead of the sub drumand a processed state thereof;

FIG. 7 is a flowchart showing a method for assembling drums of a washingmachine according to an embodiment of the present invention;

FIG. 8 is a schematic view showing a washing machine having a drum whoserotation shaft is inclined according to another embodiment of thepresent invention;

FIG. 9 is a schematic view showing motion of laundry inside the washingmachine;

FIG. 10 is a schematic view showing motion of laundry at part A of FIG.9;

FIGS. 11 to 14 are schematic views showing different exemplaryembodiments of shielding a gap between a main drum and a sub dram;

FIG. 15 is a schematic view of a washing machine showing a case that therotation shaft of the drum is inclined and a case that a lifter has aninclination in accordance with another exemplary embodiment;

FIG. 16A is a perspective view showing a first example of a main drumlifter;

FIG. 16B is a perspective view showing a second example of a main drumliter, formed shorter than the example of FIG. 16A

FIG. 17A is a perspective view showing an example of a sub drum lifterin which a straight line type inclination has been applied;

FIG. 17B is a perspective view showing an example of a sub drum lifterin which a curve type inclination has been applied;

FIG. 18 is a view showing a driving motor applied to the washingmachine;

FIG. 19 is a view showing an outer diameter of a stator and an outerdiameter of a rotor of a permanent magnet motor according to the presentinvention;

FIG. 20 is a graph showing torque when a ratio between an outer diameterof a rotor and an outer diameter of a stator is in the range of 0.7˜0.8;

FIG. 21 is a view showing a dimension of a teeth extension portion ofrotor teeth according to the present invention;

FIGS. 22 and 23 are views showing minimized cogging torque and torqueripple through gap adjustment between teeth extension portions of rotorteeth according to the present invention;

FIGS. 24 and 25 are views showing an angle between rotor teeth and alinear part of a teeth extension portion according to the presentinvention;

FIG. 26 is a planar view showing an arrangement for fabricating rotorteeth of a driving motor in a punching manner according to the presentinvention;

FIG. 27 is a partial view showing a stator and a rotor of a drivingmotor according to the present invention;

FIG. 28 is a partially detailed view showing a cut recess, a cut holeand an outer circumferential curvature of rotor tooth of a driving motoraccording to the present invention;

FIG. 29A is a planar view showing a first example of rotor tooth of adriving motor according to the present invention;

FIG. 29B is a planar view showing a second example of rotor tooth of adriving motor according to the present invention;

FIG. 29C is a planar view showing a third example of rotor tooth of adriving motor according to the present invention;

FIG. 30 is a view showing a stator of a dual motor formed by coupling ofan inner stator and an outer stator of a driving motor according to thepresent invention;

FIGS. 31 and 32 are views showing a method for punching an inner statorand an outer stator in a method for fabricating a stator of a dual motoraccording to the present invention;

FIG. 33 is a schematic view showing one exemplary embodiment of an innerstator having segment type teeth in a driving motor.

FIG. 34 is a schematic view showing a process of fabricating the segmenttype teeth.

FIG. 35A is a schematic view showing a structure of an articulatedbobbin;

FIG. 35B is a schematic view showing connected state of articulatedbobbins;

FIG. 36 is a schematic view of a tooth ring.

FIG. 37 is a schematic view of an inner yoke.

FIG. 38 is a schematic view showing one exemplary embodiment of an innerstator having integral teeth in a driving motor.

FIG. 39 is a schematic view showing a process of fabricating theintegral teeth.

FIG. 40 is a flowchart showing one exemplary embodiment of a method forassembling a stator of a driving motor.

FIG. 41 is a schematic view showing an insulator of the driving motor.

FIG. 42 is a flowchart showing one exemplary embodiment of a method forfabricating a driving motor for a washing machine.

FIG. 43 is a view showing assembly of a bearing housing and a stator ofa driving motor applied to the washing machine of the present invention;

FIG. 44 is a view showing a stator coupling opening of a bearing housingof a driving motor according to the present invention;

FIG. 45 is a view showing a housing coupling hole of a stator of adriving motor according to the present invention;

FIG. 46 is a view showing a current connector and a hall sensorconnector integrally fabricated with a stator of a dual motor applied tothe washing machine of the present invention;

FIG. 47 is a block diagram showing a connected state of a currentconnector in a stator of a dual motor according to the presentinvention;

FIG. 48 is a block diagram showing a connected state of a hall sensorand a temperature sensor in a stator of a dual motor according to thepresent invention;

FIG. 49 is a schematic view of the washing machine according to thepresent invention;

FIG. 50 is a sectional view showing an inner shaft and an outer shaft ina shaft structure for a washing machine according to the presentinvention;

FIG. 51 is an external perspective view of a shaft structure accordingto the present invention;

FIG. 52A is a planar view showing a spring washer applied to the shaftstructure of the present invention;

FIG. 52B is a side view showing the spring washer of FIG. 52A;

FIG. 52C is a perspective view showing the spring washer of FIG. 52A;

FIG. 53 is a sectional view of an inner shaft and an outer shaft in ashaft structure according to still another embodiment of the presentinvention;

FIG. 54 is a view showing assembly of a bearing housing and a stator ofa dual motor applied to the washing machine of the present invention;

FIG. 55 is a view showing a stator coupling opening of a bearing housingof a dual motor applied to the washing machine of the present invention;

FIG. 56 is a view showing a housing coupling hole of a stator of a dualmotor applied to the washing machine of the present invention;

FIG. 57 is a schematic view showing that laundry is automatically drawnout of the washing machine;

FIG. 58 is a flowchart showing an operation method for the washingmachine;

FIG. 59 is a block diagram showing a structure for controlling drums ofthe washing machine;

FIG. 60A is a schematic view showing a first example of relativerotations of the main drum and the sub drum under control of FIG. 59;

FIG. 60B is a schematic view showing a second example of relativerotations of the main drum and the sub drum under control of FIG. 59;

FIG. 60C is a schematic view showing a third example of relativerotations of the main drum and the sub drum under control of FIG. 59;

FIG. 61 is a flowchart showing an operation method for the washingmachine;

FIG. 62 is a flowchart showing a control method for a washing machineaccording to a laundry amount according to the present invention;

FIG. 63 is a block diagram showing a schematic configuration of a motordriving apparatus of a washing machine according to an embodiment of thepresent invention;

FIG. 64 is a graph showing an operation for initially driving a drivingmotor according to an embodiment of the present invention;

FIG. 65 is a graph showing a temperature change of a driving motoraccording to the order of initially driving an outer rotor and an innerrotor;

FIGS. 66 to 69 are flowcharts schematically showing a method forcontrolling a washing machine according to embodiments of the presentinvention;

FIG. 70 is a graph showing an operation to detect a laundry amount bybraking an outer rotor and an inner rotor using generated poweraccording to the present invention;

FIG. 71 is a graph showing changes of currents applied to the outerrotor and the inner rotor of FIG. 70;

FIG. 72 is a graph showing an operation to detect a laundry amount bybraking an outer rotor using redundant power and by braking an innerrotor using generated power according to the present invention;

FIG. 73 is a graph showing changes of currents applied to the outerrotor and the inner rotor of FIG. 72;

FIG. 74 is a block diagram schematically showing a configuration of amotor driving apparatus for a washing machine according to anotherembodiment of the present invention; and

FIGS. 75 and 76 are flowcharts schematically showing a laundry amountdetecting method for a washing machine according to the presentinvention.

FIGS. 77 to 80 are schematic views showing a sub-drum according toanother embodiment of the present invention.

DETAILED DESCRIPTION OF THE DISCLOSURE

Description will now be given in detail of the exemplary embodiments,with reference to the accompanying drawings. For the sake of briefdescription with reference to the drawings, the same or equivalentcomponents will be provided with the same reference numbers, anddescription thereof will not be repeated.

FIG. 1 is a schematic view of a washing machine in accordance with oneexemplary embodiment. As shown in FIG. 1, a washing machine may includea cabinet 10 defining an outer appearance corresponding to a main body.A front surface of the cabinet 10 is shown having an introductionopening 20 for introducing clothes (laundry) as a target to be washed(hereinafter, referred to as ‘laundry’) into the cabinet 10.

The introduction opening 20 may be open or closed by a door rotatablyfixed onto the cabinet. A control panel 30, which has variousmanipulation buttons for manipulating the washing machine, may belocated at an upper portion of the cabinet 10, and a detergent supplyunit (not shown) for filling the detergent may be provided at one sideof the control panel 30.

An accommodation space formed within the cabinet 10 is shown having acylindrical tub 40 for storing washing water, and a main drum 50 and asub drum 60 both rotatably installed inside the tub 40 and receiving thelaundry therein. A driving motor 70 for driving the main drum 50 and thesub drum 60, may be disposed at the rear of the tub 40.

The tub 40 may be in a cylindrical shape, and receive therein the maindrum 50 and the sub drum 60. The front face of the tub 40 may be open soas to communicate with the introduction opening 20 of the cabinet 10.Therefore, a gasket, which encompasses the front face part of the tuband the introduction opening of the cabinet, may be located between thefront face part of the tub and the introduction opening of the cabinet,whereby washing water contained in the tub can be prevented from flowinginto the cabinet.

The main drum 50 may be in a cylindrical shape, rotatably mounted in thetub 40. The main drum 50 may include a plurality of through holes formedthrough a side surface thereof such that washing water can flow outtherethrough.

The sub drum 60 may be in a cylindrical shape, rotatably mounted in themain drum 50. Here, the sub drum 60 may be mounted to be relativelyrotatable with respect to the main drum 50. That is, the main drum andthe sub drum may be driven independent of each other, which allows forvarious relative rotations according to rotation speed and rotationdirection of each drum.

The driving motor 70 is a component for generating a driving force todrive the main drum and the sub drum, and mounted at a rear surface ofthe tub 40. The driving motor 70 may include a secured stator 71, anouter rotor 72 rotatable outside the stator, and an inner rotor 73rotatable inside the stator. Such driving motor having the two rotorsmay be referred to as a dual-rotor motor for convenience.

FIG. 4 shows the driving motor 70 in more detail. As shown in FIG. 4,the stator 71 has an annular structure to surround the inner rotor 73,and is fixedly coupled to the tub side. FIG. 5 schematically shows astructure capable of transferring a driving force from the driving motorto the main drum and the sub drum. As shown in FIGS. 4 and 5, the innerrotor 73 may be rotatably disposed inside the stator 71, and connectedto an outer shaft 81, which will be explained later, so as to getinvolved in the rotation of the main drum 50. The outer rotor 72 may berotatably disposed outside the stator 71 and connected to an inner shaft82, which will be explained later, so as to get involved in the rotationof the sub drum 60. Each of the inner rotor and the outer rotor mayinclude magnets, and accordingly be rotated by magnetic fields generatedby current when such current is applied to the inner and outer windingportions of the driving motor.

Upon controlling the current flowing on coils wound on inner and outerteeth, the inner rotor and the outer rotor may be rotated independent ofeach other. Accordingly, referring to FIG. 5, the single driving motor70 may allow for the mutually independent rotations of the main drum 50and the sub drum 60. Namely, the driving motor may independently drivethe main drum and the sub drum.

With the configuration, the main drum and the sub drum are drivenindependently by the driving motor to induce rotations of the laundry bythe difference in relative rotation speed between the drums, therebygenerating three-dimensional (3D) motions of the laundry while thelaundry rotates in the drums.

FIGS. 2 and 3 show coupled states between shafts and drums in moredetail. Referring to FIGS. 2 and 3, the outer shaft 81 may be insertedthrough the tub to connect the inner rotor 73 to the main drum 50. Theouter shaft 81 corresponds to a hollow shaft, so the inner shaft 82 maybe mounted inside the outer shaft 81. The inner shaft 82 may be insertedthrough the outer shaft 81 to connect the outer rotor 72 to the sub drum60.

The main drum 50 and the outer shaft 81 may be connected by a main drumspider 91. Referring to FIG. 2, the main drum 50 may have openings at afront side 51 and a rear side 52. The main drum spider 91 may be coupledto the outer shaft 81 and fixed to the main drum 50. The sub drum 60 andthe inner shaft 82 may be connected by a sub drum spider 95. The subdrum 60 may include a sub drum back forming its rear surface. The subdrum 60 may have the front side open and the rear side closed by the subdrum back. The sub drum spider 95 may be closely adhered onto the subdrum back.

Referring to FIG. 2, the main drum spider 91 may include a shaftcoupling portion 92 coupled to the outer shaft, a spider supportingportion 93 radially extending from the shaft coupling portion 92, and adrum fixing portion 94 provided at an end of the spider supportingportion 93. Here, the drum fixing portion 94 may be fixedly coupled tothe main drum 50. The shaft coupling portion 92 may be formed at acentral part of the main drum spider 91, and have a coupling groove towhich the outer shaft 81 is coupled. The spider supporting portion 93may include a plurality of cantilevers radially extending from thecentral part. The drum fixing portion 94 may have a ring shape forconnecting ends of the spider supporting portion 93. The spidersupporting portion 93 may support the main drum spider so as to allow adriving force to be transferred to the main drum upon transferring thedriving force transferred from the outer shaft 81 to the main drum viathe main drum spider. Alternatively, as an exemplary variation, thespider supporting portion 93 may be formed in a disk shape extendingfrom the shaft coupling portion.

The main drum spider 91 may be coupled to an outer circumferentialsurface of the main drum. That is, the drum fixing portion 94 in thering shape may be fixed to an end portion of the outer circumferentialsurface of the main drum. The coupling of the drum fixing portion 94 andthe outer circumferential surface of the main drum may be implemented,for example, by screws or by welding. As an exemplary variation of theone exemplary embodiment, the main drum may include a bent portion bentfrom a rear end thereof toward the central part, and the drum fixingportion of the main drum spider may be coupled to the bent portion. Thesub drum 60 and the inner shaft 82 may be connected by the sub drumspider 95. Still referring to FIG. 2, the sub drum 60 may have a subdrum back 62 forming its rear surface. The sub drum 60 may have thefront side open and the rear side closed by the sub drum back 62. Thesub drum spider 95 may be closely adhered onto the sub drum back 62.

The sub drum spider 95 may include a shaft coupling portion 96 coupledto the inner shaft 82, and a plurality of drum fixing portions 97radially extending from the shaft coupling portion 96. Here, ends of thedrum fixing portions 97 may be fixed to the sub drum back 62. The subdrum back 62 may further include a receiving portion 63 recessedinwardly in correspondence with the shape of the sub drum spider 95. Thesub drum spider 95 may be received in the receiving portion 63 to beclosely adhered onto the sub drum back 62. The coupling of the drumfixing portions 97 and the sub drum back 62 may be implemented, forexample, by screws or by welding.

Referring to FIGS. 2 and 3, the sub drum spider 95 may be providedbetween the sub drum back 62 and the main drum spider 91. However, thesub drum spider 95 can integrally rotate with the sub drum back 62 andindependently rotate with respect to the main drum spider 95. That is,the sub drum spider 95 may rotate independent of the main drum spider91, which allows the main drum 50 and the sub drum 60 to rotateindependent of each other. The foregoing configurations provide thestructure of the washing machine that each drum can independently bedriven by the single driving motor.

Referring to FIG. 5, the outer shaft and the inner shaft may have amutually independently rotatable structure with interposing a bearingtherebetween. The outer rotor and the inner rotor may also have themutually independently rotatable structure with interposing the statortherebetween. The stator may include winding portions separately at theouter rotor side and the inner rotor side, which allows the drivingmotor to independently rotate the outer rotor and the inner rotor.Hence, the main drum may be driven by the inner rotor and the sub drummay be driven by the outer rotor, so the main drum and the sub drum canbe driven independently by virtue of the driving motor. Also, theindependent driving of the outer rotor and the inner rotor may enablethe main drum and the sub drum to perform various relative rotations.That is, such various relative rotations can be generated by making arotation direction different or making speed different in the samerotation direction.

As an exemplary variation of the exemplary embodiment, the main drum andthe sub drum may include a main drum back and a sub drum back,respectively, forming their rear surfaces. Here, both the main drum andthe sub dram may have the front side open and the rear side closed bythe main drum back and the sub drum back, respectively. Here, the maindrum spider may be fixed onto the main drum back. Also, the sub drumspider may be fixed onto the sub drum back. The sub drum spider may beprovided between the sub drum back and the main drum back. Here, the subdrum spider may integrally rotate with the sub drum back andindependently rotate with respect to the main drum back.

An outer circumferential surface of the sub drum may face a part of aninner circumferential surface of the main drum. That is, an innercircumferential surface of the main drum and the inner circumferentialsurface of the sub drum may have different lengths in an axialdirection, and the outer circumferential surface of the sub drum mayface a part of an inner circumferential surface of the main drum.Preferably, a structure that the sub drum is shorter than the main drumin view of the length in the axial direction is provided.

FIG. 1 and FIG. 5 schematically show the main drum and the sub drum withthe structure. Referring to FIG. 5, the inner circumferential surface ofthe main drum and the inner circumferential surface of the sub drum mayhave different lengths in an axial direction. Hence, the sub drum 60 maybe mounted inside the main drum 50 so as to extend from one end portionof the main drum 50 in an axial direction, and the main drum 50 may bedisposed such that only a part of its inner circumferential surfacefaces the outer circumferential surface of the sub drum. In thisstructure, the laundry may contact an interface (boundary surface)between the sub drum and the main drum, and accordingly rotate in onedirection due to the difference in the rotation speed between the drums.Here, the laundry may be rotated based on a perpendicular rotation shaftwhen viewed from the inner circumferential surface of the drums. Inaddition, the laundry may generate a motion in a circumferentialdirection of the drum (i.e., circumferential-direction motion) due tothe friction against the inner circumferential surface of the drum.Accordingly, the laundry may move in the circumferential direction ofthe drum and rotate based on the rotating shaft perpendicular to theinner circumferential surface of the drum, thereby performing motions inthe axial direction (i.e., axial-direction motion) from a drum siderotated at fast speed to a drum side rotated at slow speed. Theaxial-direction motion is generated as the laundry rotates based on therotating shaft perpendicular to the inner circumferential surface of thedrum. Consequently, the laundry may perform 3D motions by virtue of theaxial-direction motion in addition to the two-dimensionalcircumferential-direction motion.

Referring to FIG. 3 and FIG. 5, the structure that the sub drum isshorter than the main drum in view of the length in the axial directionis provided. Here, the sub drum may be mounted inside the main drum toextend from one end portion of the main drum in an axial direction.Accordingly, an outer circumferential surface 60 a of the sub drum mayface an inner circumferential surface 50 b of the main drum such thatonly a part 50 b of the inner circumferential surfaces 50 a and 50 b ofthe main drum 50 can face the outer circumferential surface 60 a of thesub drum 60. In more detail, referring to FIG. 3, a ratio (D2/D1) of alength D2 of the inner circumferential surface of the sub drum in anaxial direction with respect to a length D1 of the inner circumferentialsurface of the main drum in an axial direction may be 0˜0.5. That is,the length of the inner circumferential surface of the sub drum in theaxial direction may be shorter than a half of the length of the innercircumferential surface of the main drum in the axial direction.

More preferably, the radio (D2/D1) of the length D2 of the innercircumferential surface of the sub drum in the axial direction withrespect to the length D1 of the inner circumferential surface of themain drum in the axial direction may be ⅓, which is experimentallyderived to cause an optimal 3D motion of the laundry in consideration oftorque distribution due to driving two drums, a mechanical force appliedto the laundry and overall movements of the laundry. To describe this ina different manner, the inner circumferential surface of the main drummay be divided into a first surface 50 a that does not face the outercircumferential surface of the sub drum and the second surface 50 b thatfaces the outer circumferential surface of the sub drum. In this case,the radio (D2/d1) of the length D2 of the inner circumferential surface60 b of the sub drum in the axial direction with respect to the lengthd1 of the first surface 50 a in the axial direction may be 0.5.

From the perspective of the configuration, a structure that the laundrycan contact (be positioned at) an interface between the sub drum and themain drum is provided. FIG. 9 shows the motion of the laundry within thedrums merely by illustrating the first surface 50 a of the main drum andthe inner circumferential surface 60 b of the sub drum with which thelaundry is contactable. FIG. 10 is an enlarged view of an interface Awhere the first surface 50 a of the main drum and the innercircumferential surface 60 b of the sub drum are divided. The laundrymay generate a motion of being unidirectionally rotated due to adifference in rotation speed between the drums. Referring to FIG. 9, themain drum rotates in a counterclockwise direction and the sub drumrotates in a clockwise direction. Here, it may be preferable that anabsolute value of the rotation speed of the sub drum is greater than anabsolute value of the rotation speed of the main drum. If the absolutevalues are the same, the laundry may rotate at the same place at theinterface A between the main drum and the sub drum. Therefore, for the3D motions of the laundry, it may be preferable to make those drumsrotated at different speeds such that much rotational force can beapplied in a single direction.

As aforementioned, FIG. 10 shows the motion of the laundry in thevicinity of the interface A between the drums when the rotation speed ofthe sub drum is faster than the rotation speed of the main drum. Here,the laundry may rotate in a clockwise direction B centering around aperpendicular rotation shaft Z, when viewed from the innercircumferential surface of the drum. Also, the laundry may performcircumferential-direction motions due to friction against the innercircumferential surfaces of the drums. Accordingly, the laundry canrotate centering around the rotation shaft perpendicular to the innercircumferential surface of the drum with moving in the circumferentialdirection of the drum (i.e., performing the circumferential-directionmotion), thereby performing an axial-direction motion D from the fastrotating drum 60 to the slowly rotating drum 50.

The axial-direction motion D of the laundry may be generated by mutuallyrelative rotations between the main drum and the sub drum. In moredetail, the inner circumferential surface of the main drum is dividedinto the first surface 50 a that does not face the outer circumferentialsurface of the sub drum and the second surface 50 b that faces the outercircumferential surface 60 a of the sub drum. Accordingly, the laundrymay be rotated (moved) in the axial direction by the relative motionsbetween the first surface 50 a of the inner circumferential surface ofthe main drum and the inner circumferential surface 60 b of the subdrum. From the perspective of the laundry, the laundry may move in thecircumferential direction in response to the rotations of the main drumor the sub drum and move in the axial direction in response to therelative motions between the main drum and the sub drum. Here, theaxial-direction motion of the laundry may be made by the rotations ofthe laundry in response to the relative motions between the main drumand the sub drum. In more detail, the axial-direction motion D is causedby the rotations of the laundry based on the rotation shaft Zperpendicular to the inner circumferential surface of the drum.Accordingly, the laundry may be allowed for the axial-direction motion Dof the drum in addition to the two-dimensional (2D)circumferential-direction motion D, which results in realization of the3D motions of the laundry.

The arrow in FIG. 9 schematically indicates the 3D motion of the laundrywithin the drums. Referring to FIG. 9, the laundry shows a shape of aschematically twisted band, which is a motion shape resulted from thelaundry generating the circumferential-direction motion and a fallingmotion by the force of gravity with rotating within the drums. From theperspective of the aforesaid configuration, the main drum and the subdrum can be driven by the driving motor, independently of each other, soas to cause the laundry to be rotated by the difference in the rotationspeed between the drums, thereby enabling the laundry to perform the 3Dmotions with rotating within the drums.

Also, as the sub drum has the length in the axial direction shorter thanthe main drum, the laundry can contact the interface between the subdrum and the main drum, and accordingly, generate the motion of beingrotated by the difference in the rotation speed between the drums, whichresults in realization of the 3D motions of the laundry. Consequently,the realization of the 3D motions of the laundry may arouse improvementof washing efficiency and reduction of a washing time of the washingmachine. A washing machine in accordance with another exemplaryembodiment shown in FIG. 1 has a structure that the rotation shaft ofthe drums is perpendicularly disposed. However, the present disclosuremay not be limited to the structure. A washing machine may alternativelyhave a structure that a rotation shaft of drums is inclined by apredetermined angle. FIG. 8 shows an exemplary embodiment of thestructure that the rotation shaft is inclined. This structure may derivemore various movements of the laundry in response to the rotations ofthe main drum and the sub drum. That is, when the laundry is fallen froman upper side of the drums by the force of gravity while moving in thecircumferential direction along the inner circumferential surfaces inresponse to the rotations of the main drum or the sub drum, the laundryis fallen on a position out of the existing circumferential directionroute. Accordingly, the axial-direction motion may be enabled by theforce of gravity, resulting in more efficient motions of the laundry.

Hereinafter, a structure of a sub drum and a coupling method thereofwill be described in detail with reference to FIGS. 77 to 80. A sub drum60′, 60″ may include a cylindrical portion forming an outercircumferential portion, and a drum back disposed on a rear surfacethereof and coupled with a sub drum spider. Each drum back may include areceiving portion 63 a, 63 b recessed toward a front side such that thesub drum spider is received therein. A spider 95 a, 95 b may include aplurality of cantilevers radially extending from a center of an innershaft, being coupled to the drum back of the sub drum 60′, 60″.

As one exemplary embodiment, FIGS. 77 and 78 show a sub drum having anintegral structure of a cylindrical portion and a drum back. As shown inFIGS. 6 and 7, the sub drum 60′ may have the cylindrical portion and thedrum back which are integrally formed with each other as one member.When molding the sub drum 60′ using the one integral member, severaladvantages may be obtained, such as an increased strength of the member,and improved durability due to non-existence of separate coupling. Also,vibration may be reduced or avoided because any collision is not causedbetween assembly components due to vibration, which is generated duringhigh speed rotation of the drum of the washing machine.

In this exemplary embodiment, since the sub drum 60′ has to be moldedusing the one member, a contact portion between the cylindrical portionof the sub drum and the outer circumference of the drum back should beformed in a curved form. Accordingly, an inner space of the sub drum 60′may have a slightly small capacity due to the curved portion. With theintegral structure of the sub drum 60′, the inner capacity of the drumof the washing machine may be designed by approximately 90 L. Also, thesub drum 60′ is fabricated using one member in this exemplaryembodiment. This may make it difficult to form drain openings orpatterns at the sub drum. Referring to FIG. 78, the receiving portion 63a may include spider coupling openings 63 aa for coupling of the subdrum spider 95 a. The sub drum spider 95 a may have coupling openingscorresponding to the coupling openings 63 aa of the receiving portion 63a.

The receiving portion 63 a may receive the sub drum spider 95 a havingthe plurality of radial cantilevers such that a rotational force of thespider can be transferred to the sub drum. The sub drum spider 95 a maybe firmly coupled, by coupling bolts or the like, with being inserted inthe receiving portion 63 a. To this end, the receiving portion 63 a mayhave the coupling openings 63 aa, and the spider 95 a may have thecorresponding coupling openings (not shown in the drawing).

Referring to FIG. 78, preferably, the receiving portion 63 a may beformed not to reach (contact) the outer circumference of the sub drum,and the cantilevers of the sub drum spider 95 a may be formed to besmaller than a radius of the sub drum back so as to be inserted into thereceiving portion. As another exemplary embodiment, FIGS. 79 and 80 showa sub drum having an independent structure of a cylindrical portion anda drum back. As shown in FIGS. 79 and 80, a sub drum 60″ may have acylindrical portion 61 b and a drum back 62 b as independent members ofeach other. The drum back 62 b may be coupled to an outer circumferenceof a rear side of the cylindrical portion 61 b to close the rear side.Referring to FIG. 80, for coupling of the assembly type sub drum, drumback coupling openings 61 bb may be formed at a rear end portion of thecylindrical portion 61 b, and the outer circumference of the drum back62 b may be bent in a lengthwise direction of the drum. Cylindricalportion coupling openings 62 bb may be formed at the bent portion.

With the structure of the assembly type sub drum, the drum back 62 b andthe cylindrical portion 61 a may be firmly coupled to each other bycoupling bolts or the like with the coupling openings 61 bb and thecoupling openings 62 bb aligned with each other. Also, the receivingportion 63 b of the drum back 62 b may extend up to the outercircumference of the drum back 62 b. The cantilevers of the sub drumspider 95 b may extend up to the outer circumference of the sub drumback 62 b, and end portions of the cantilevers of the sub drum spider 95b may be coupled to the rear outer circumference of the cylindricalportion 61 b. Preferably, as shown in FIG. 80, the end portions of thecantilevers of the sub drum spider 95 b may be integrally firmlyassembled by use of coupling bolts or the like, which are insertedthrough the coupling openings 61 bb and 62 bb from the bent portion ofthe outer circumference of the drum back 62 b.

In accordance with the exemplary embodiment shown in FIGS. 8 and 9,comparing with the sub drum with the integral structure, the greaterinner space of the drum of the washing machine may be ensured becausethe curved portion may not have to be formed at the contact portionbetween the cylindrical portion 61 b and the outer circumference of thedrum back 62 b. When applying the assembly type sub drum of thisexemplary embodiment to a dual drum washing machine, an inner space witha capacity of about 94 L may be ensured, increasing the capacity of thesub drum by approximately 4 L as compared with the integral type subdrum. Also, in this exemplary embodiment, the sub drum 60″ may befabricated by assembling the cylindrical portion with the drum back.Accordingly, the processing task such as forming drain openings orpatterns at each member may be performed prior to an assembly process.Consequently, the processing of the drain openings and patterns may befacilitated as compared to the sub drum with the integral structure.

However, this exemplary embodiment may allow the independent members tobe assembled with each other to fabricate the sub drum 60″. This may bedisadvantageous as compared to the one integral member in view of theassembly strength of the members. Also, the collision between assemblycomponents may be caused due to vibration generated during high speedrotation of the drum of the washing machine. This may have adisadvantage in view of vibration. Another exemplary embodiment of thepresent disclosure may provide a method for assembling an assembly typesub drum structure shown in FIGS. 79 and 80.

As shown in FIG. 80, a method for assembling a sub drum of a washingmachine may include coupling the drum back 62 b, which is disposed onthe rear surface of the sub drum and coupled with the sub drum spider 95b, to the cylindrical portion 61 b which forms the outer circumferentialportion of the sub drum 60″. Next, the method may further includereceiving the sub drum spider 95 b in the spider receiving portion 63 brecessed toward the front of the drum back 62 b, and coupling the endportions of the cantilevers of the sub drum spider 95 b by insertingbolts through the coupling openings formed at the rear end portion ofthe cylindrical portion 61 b of the sub drum and the curved outercircumference of the drum back 62 b, respectively.

Meanwhile, referring to FIG. 3, the inner circumferential surface of themain drum is shown having a drum guide 55 to seal an interval from theouter circumferential surface of the sub drum. The drum guide 55 may beprovided along the inner circumferential surface of the main drum andseal the interval from the outer circumferential surface of the subdrum. This is for preventing the laundry from being jammed between thedrums.

Referring to FIG. 3, the sub drum is smaller than the main drum inradius. The sub drum may accordingly be mounted within the main drum.Hence, some interval may be generated between the inner circumferentialsurface of the main drum and the inner circumferential surface of thesub drum.

FIG. 11 shows an exemplary embodiment of the drum guide. The drum guide55 may include a body portion 56 coupled onto the inner circumferentialsurface of the main drum to protrude into the main drum, and a guideportion 57 extending toward the inner circumferential surface of the subdrum. As aforementioned, the interval is generated between the innercircumferential surface of the main drum and the inner circumferentialsurface of the sub drum. The guide portion 57 of the drum guide 55 mayseal the interval by extending up to the inner circumferential surfaceof the sub drum. That is, the inner circumferential surface of the maindrum and the inner circumferential surface of the sub drum form adiscontinuous surface due to the difference in radius. The drum guidecan allow those inner circumferential surfaces to be continuous.Accordingly, the laundry may be prevented from being damaged due tobeing jammed into the interface between the drums even though generatingthe aforementioned axial-direction motion in the drums. Especially, whentwo drums are independently driven as shown in the washing machine ofthis specification, the main drum and the sub drum perform the relativerotations. Thus, when the laundry is jammed into the interface, theremay be much room for causing damage on the laundry, so the drum guidecan be more efficient for protection of the laundry.

More preferably, the body portion 56 may have an inclination or curvedsurface to some degree, thereby forming an easy inclination orcontinuous surface from the bottom surface of the main drum up to theguide portion 57. With this configuration, the resistance with respectto the axial-direction motion of the laundry within the drums can bereduced, resulting in more smooth motions of the laundry.

Also, a reinforcing bead 65 for preventing torsion of the sub drum maybe provided on the inner circumferential surface of the outercircumferential surface of the sub drum. Referring to FIG. 11, the subdrum 60 may preferably be provided with the reinforcing bead 65protruding into the sub drum along the circumferential surface withbeing spaced apart from an end portion of the sub drum with apredetermined interval. Of course, the reinforcing bead 65 may protrudetoward the outer circumferential surface of the sub drum. Thereinforcing bead 65 may serve to prevent the torsion of the drum byreinforcing the strength of the sub drum. Here, the guide portion of thedrum guide may extend up to the bead of the sub drum. Therefore, thebead for reinforcing the strength of the sub drum can prevent the innercircumferential surface of the sub drum from being discontinuous, andform the continuous surface to be helpful for the motions of thelaundry.

FIG. 12 shows another exemplary embodiment of the drum guide. Referringto FIG. 12, the sub drum 60 may include a bead 65 protruding to theoutside of the sub drum along the circumferential surface with beingspaced apart from an end portion 61 of the sub drum 60 with apredetermined interval. The guide portion 57 of the drum guide 55 mayextend upon the end portion 61 of the sub drum. Unlike theaforementioned exemplary embodiment, the bead 65 does not protrude intothe sub drum, so the guide portion 57 does not have to extend up to thebead 65. Hence, the guide portion 57 of the drum guide 55 may extendonly up to the end portion 61 of the sub drum. This configuration mayprevent the laundry from being jammed into the interface where the maindrum and the sub drum independently driven by the drum guide perform therelative rotations.

FIGS. 11 and 12 show that the end portion 61 of the sub drum is curledto the outside along the circumferential surface. This is for preventingthe laundry from being jammed due to the end portion of the sub drum byway of processing the end portion of the sub drum to have a curvedsurface. FIG. 13 shows another exemplary embodiment of a washingmachine. Referring to FIG. 13, the main drum 50 may be divided into afirst portion 50 a and a second portion 50 b having different innerdiameters from each other. Here, the inner diameter of the first portion50 a may be the same as the inner diameter of the sub drum, and theinner diameter of the second portion 50 b may be greater than an outerdiameter of the sub drum 60. This is intended to extend the part (i.e.,50 b) of the main drum such that the radius of the portion 50 a of themain drum can be the same as the radius of the inner circumferentialsurface of the sub drum, whereby the inner circumferential surface ofthe main drum and the inner circumferential surface of the sub drum canbe flush with each other. Here, the sub drum may be mounted inside thesecond portion 50 b of the main drum, to be rotatable within the maindrum. Here, the end portion 61 of the sub drum may also be curled to theoutside along the circumferential surface, with being located within thesecond portion 50 b.

With the configuration, the structure of preventing the laundry frombeing jammed is produced during formation of the drums without use of aseparate guide or the like, thereby shielding the interface between themain drum and the sub drum. Also, the inner circumferential surfaces ofthe main drum and the sub drum where the laundry contacts can becontinuous, thus to reduce resistance against the motions of thelaundry, thereby making the laundry moved (rotated) more smoothly. Inthe meantime, FIG. 14 shows another exemplary embodiment of a washingmachine. As shown in FIG. 14, the main drum 50 may further include adrum guide unit 58 protruding into the drum along the innercircumferential surface thereof. In this structure, the innercircumferential surface of the drum guide unit 58 is flush with theinner circumferential surface of the sub drum, thereby shielding theinterface between the main drum and the sub drum. The end portion of thesub drum may also be curled to the outside along the circumferentialsurface, with being located outside more than the inner circumferentialsurface of the drum guide unit.

A place (position) where the laundry is jammed or the motion of thelaundry is disturbed is where an interval is formed due to a differencein radius between the main drum and the sub drum. Hence, the part of themain drum may be formed to protrude before the interface where theinterval is formed. Such protruded part may allow the radiuses of theinner circumferential surfaces of the main drum and the sub drum to bethe same at the interface between the main drum and the sub drum and beflush with each other. Consequently, the inner circumferential surfacesof the main drum and the sub drum that the laundry contacts may become acontinuous surface, whereby the laundry cannot be easily jammed into theinterface and the resistance against the motions of the laundry can bereduced, resulting in more smooth motions of the laundry. The structureof preventing the jamming of the laundry can also be produced during theformation of the drums without use of a separate guide or the like.Referring to FIG. 1, a plurality of main drum lifters 101 are protrudingfrom an inner circumferential surface of the main drum toward the insidein a radial direction, and a plurality of sub drum lifters 102 areprotruding from an inner circumferential surface of the sub drum towardthe inside in a radial direction. This may allow laundry to smoothlymove in the drum.

An inner circumferential surface of the main drum may be divided into afirst surface 50 a not facing an outer circumferential surface of thesub drum, and a second surface 50 b facing the outer circumferentialsurface of the sub drum. The main drum lifters 101 are provided on thefirst surface 50 a. The main drum lifters 101 may be disposed with thesame interval therebetween along an inner circumferential surface of themain drum. And, the sub drum lifters 102 may be disposed with the sameinterval therebetween along an inner circumferential surface of the subdrum. A plurality of lifters are provided on the inner circumferentialsurface of the drum so that laundry inside the drum may perform 3Dmotions.

A length ratio of the main drum lifters 101 and the sub drum lifters 102in an axial direction may be proportional to a length of the firstsurface 50 a of an inner circumferential surface of the main drum, and alength of an inner circumferential surface 60 a of the sub drum.Referring to FIG. 3, a length of the main drum lifters 101 in an axialdirection may be defined as ‘l1’, a length of the sub drum lifters 102in an axial direction may be defined as ‘l2’, a length of the firstsurface 50 a of the inner circumferential surface of the main drum maybe defined as ‘d1’, and a length of the inner circumferential surface 60a of the sub drum may be defined as ‘d2’. In this case, a ratio of l1:l2may be proportional to a ratio of d1:d2. This is in order torespectively provide the lifters at the main drum and the sub drumhaving different lengths in an axial direction, and to allow the liftersto effectively contact laundry.

Referring to FIG. 3, the main drum lifters 101 and the sub drum lifters102 are provided in the drum in parallel with an axial direction.However, the present disclosure is not limited to this. For instance,the main drum lifters and the sub drum lifters may be disposed with apredetermined angle from an axial direction. FIG. 15 illustrates thatthe main drum lifters and the sub drum lifters are disposed with apredetermined angle from an axial direction. Referring to FIG. 15, themain drum lifters and the sub drum lifters are inclined with apredetermined angle (θ) from an axial direction. In this case, arotation direction of the main drum is determined according to an angledirection of the main drum lifters with respect to an axial direction,and a rotation direction of the sub drum is determined according to anangle direction of the sub drum lifters with respect to an axialdirection. That is, a rotation direction of the drum is determined basedon an inclined direction of the lifters so that laundry inside the drummay smoothly perform 3D motions by the lifters. When the washing machineof FIG. 15 is viewed from an introduction opening side, the main drum 50clockwise rotates but the sub drum 60 counterclockwise rotates. However,the present disclosure is not limited to this. That is, an inclinationdirection of the lifters may be controlled. Under this configuration,laundry may move in an axial direction toward the center of the drumthus to perform 3D motions when the drum rotates.

Referring to FIGS. 1 and 3, the main drum lifters 101 are backwardextending from a front end of the main drum, and the sub drum lifters102 are forward extending from a rear end of the sub drum. And, the maindrum lifters and the sub drum lifters have inclinations which becomelower toward the opposite direction. This is in order to prevent laundryto be concentratively disposed at an inner side or an outer side of thedrum due to its motions in an axial direction, but in order to allow thelaundry to be posited at the center of the drum for 3D motions of thelaundry.

FIG. 16 illustrates examples of the main drum lifters 101. Referring toFIG. 16, the main drum lifter of FIG. 16 a is longer than the main drumlifter of FIG. 16 b in an axial direction. The reason is because awashing machine to which the main drum lifter of FIG. 16 a is appliedhas a greater ratio than a washing machine to which the main drum lifterof FIG. 16 b is applied. Here, the ratio indicates a ratio of a lengthof the first surface 50 a of the inner circumferential surface of themain drum in an axial direction, with respect to a length of the innercircumferential surface 60 a of the sub drum in an axial direction.Sectional heights in a radial direction of the main drum lifters 101become lower toward a rear side of the main drum along an axialdirection. Referring to FIG. 16 viewed from an introduction opening sideof the washing machine, the main drum lifters 101 have heights whichbecome lower toward a rear side 52 from a front side 51 of the maindrum.

FIG. 17 illustrates examples of the sub drum lifters 102. Referring toFIG. 17, like the main drum lifters, the sub drum lifters may havedifferent lengths according to a ratio of a length of the first surface50 a of the inner circumferential surface of the main drum in an axialdirection, with respect to a length of the inner circumferential surface60 a of the sub drum in an axial direction. Sectional heights in aradial direction of the sub drum lifters 102 become lower toward a frontside of the sub drum along an axial direction. Referring to FIG. 17viewed from an introduction opening side of the washing machine, the subdrum lifters 102 have heights which become lower toward a front side 61from a rear side 62 of the sub drum. This configuration is implementedin order to allow laundry inside the drum to move in an axial directionthus to perform 3D motions.

The main drum lifters 101 or the sub drum lifters 102 may be formed tohave a straight inclination or a curve inclination along an axialdirection. FIG. 17 illustrates inclined sub drum lifters. Moreconcretely, FIG. 17 a illustrates a sub drum lifter to which a straightline type inclination (A) has been applied, and FIG. 17 b illustrates asub drum lifter to which a curve type inclination (B) has been applied.These various inclination types are implemented so as to allow laundryinside the drum to move in an axial direction to perform 3D motions. Inthe aspect of functions, the main drum lifters 101 and the sub drumlifters 102 may guide motions of the laundry in a circumferentialdirection. Since the lifters are protruding from an innercircumferential surface of the drum in a radial direction, laundry maybe forcibly moved in a circumferential direction of the drum accordingto rotation of the drum. Facing inclinations of the main drum liftersand the sub drum lifters may guide motions of the laundry in an axialdirection. As aforementioned, these inclinations of the lifters in anaxial direction are implemented so as to allow laundry inside the drumto move in an axial direction thus to perform 3D motions. Referring toFIG. 2, a balancer 56 for preventing vibration and an eccentric state ofthe drum may be provided at the front side 51 of the main drum.

Hereinafter, a driving motor 70 applied to the washing machine of thepresent disclosure will be explained in more details with reference tovarious embodiments. As shown in FIG. 19, a stator 2000 of a permanentmagnet motor is formed in a ring shape, and includes stator teeth 2021protruding towards the core center and stator slots 2023 each formedbetween the stator teeth 2021. A rotor 1000 is installed inside thestator 2000 in a spaced state from an inner circumferential surface ofthe stator 2000, and is formed in a ring shape. A coil (C) is wound onthe stator teeth 2021, and an induced electromotive force is generatedas current flows to the coil (C).

The rotor includes a plurality of rotor teeth 1100 disposed in a ringshape with a constant gap therebetween, and each permanent magnets (M)is installed between the rotor teeth 1100. The rotor teeth 1100 isintegrally mounted to a rotor shaft 2030 by a bushing 2040. The rotorteeth 1100 and the busing 2040 are integrally coupled to each other asan injection molding material of the bushing is inserted into a bushingside recess of the rotor teeth 1100. The stator 2000 and the rotor 1000are disposed to be concentric with each other in a spaced state fromeach other. The rotor rotates by current applied to the coil (C) woundon the stator teeth 2021, and a magnetic force of the permanent magnet(M) mounted between the rotor teeth 1100.

According to one embodiment of the present invention, there is provideda permanent magnet motor comprising: a stator 2000 including statorteeth 2021 and stator slots 2023, and fixedly-installed as a coil (C) iswound on the stator teeth 2021; and a rotor 1000 including rotor teeth1100, a permanent magnet (M) and a bushing 2040, the rotor spaced froman inner circumference of the stator 2000 and rotating centering arounda rotor shaft 2030 by a magnetic force. A ratio of an outer diameter(Dr) of the rotor 1000 with respect to an outer diameter (Ds) of thestator 2000 is in the range of 0.7˜0.8. A rotational force, torque ofthe rotor of the permanent magnet motor is calculated by the followingformula.T∝k·L·L_(st)·N_(ph)·R_(ro)·B_(g)·I  [Formula 1]

T: Torque

k: Constant

Lst: Teeth lamination height

Nph: The number of winding turns of coil

Rro: Outer diameter of rotor (=Dr)

Bg: Magnetic density of permanent magnet

I: Current applied to coil

According to the Formula 1, torque (T), a rotational force of the rotoris proportional to each lamination height (L_(st)) of stator teeth androtor teeth, and the number of winding turns (N_(ph)) of a coil. Thatis, when the lamination height (L_(st)) of the stator teeth isincreased, the amount of coil winding is increased. And, when the numberof winding turns (N_(ph)) is increased, the amount of coil winding isincreased. The reason is because the torque (T) is increased as currenthas higher intensity due to a large amount of current applied to thecoil.

The rotor torque (T) is increased as current applied to the coil woundon the outer circumference of the stator teeth is increased. Therefore,current (I) applied to the coil, the teeth lamination height (L_(st))and the number of winding turns (N_(ph)), serve as factors to increasethe intensity of current. A magnetic force of the permanent magnet (M)is increased in proportion to magnetic density (B_(g)) of the permanentmagnet of the rotor, and an outer diameter of the rotor (R_(ro)=D_(r)).Therefore, the torque (T) of the rotor is increased in proportion to theouter diameter of the rotor (R_(ro)=D_(r)) and the magnetic density(B_(g)) of the permanent magnet.

In an assumption that the teeth lamination height (L_(st)), the magneticdensity (B_(g)) of the permanent magnet, and the intensity of current(I) applied to the coil are constant, the intensity of the torque (T)can be increased by two factors, the number of winding turns (N_(ph))and the outer diameter of the rotor (R_(ro)=D_(r)). Generally, apermanent magnet motor applied to a washing machine has a limited size.Therefore, the teeth lamination height (L_(st)) and the outer diameter(D) of the stator 2000 are limited to some degrees. Furthermore, sincethe magnetic density (B_(g)) of the permanent magnet and the intensityof current (I) can be arbitrarily input from the outside, they areexcluded from the factors when designing the permanent magnet motor ofthe present invention. Under this configuration, the intensity of torque(T) can be determined by the number of winding turns (N_(ph)) and theouter diameter of the rotor (R_(ro)=D_(r)). The number of winding turns(N_(ph)) is proportional to the length of the stator teeth 2021 of FIG.19, which is determined by a ratio between the diameter of the rotor(D_(r)) and the outer diameter (D_(s)) of the stator (D_(r)/D_(s)).

FIG. 20 is a graph showing a torque value (N·m) of the motor accordingto the ratio between the diameter of the rotor (D_(r)) and the outerdiameter (D_(s)) of the stator (D_(r)/D_(s)), in a state where theintensity of current (I) applied to the coil has three different values.Referring to FIG. 20, the torque value is maximum when the ratio(D_(r)/D_(s)) is in the range of 0.7˜0.89. In the present invention, therotational force of the permanent magnet motor is maximized when theratio between the diameter of the rotor (D_(r)) and the outer diameter(D_(s)) of the stator (D_(r)/D_(s)) is maintained in the range of0.7˜0.8. According to another embodiment of the present invention, therotor teeth 1100 includes teeth extension portions 1110 protruding fromthe right and left sides of the rotor teeth 1100 in an outer diameterdirection. The end of the teeth extension portion 1110 has a height (DH)less than 0.3 mm, and a distance (DW) between teeth extension portions1110 of neighboring rotor teeth 1100 is in the range of 5.5 mm˜6.5 mm.Preferably, an outer diameter end portion of the rotor teeth 1100 isformed such that the rotor teeth 1100 have an arc angle of 60°.

Referring to FIG. 21, the rotor teeth 1100 of the present invention isprovided with teeth extension portions 1110 protruding from the rightand left sides of the rotor teeth 1100 in an outer diameter direction.An upper surface of the teeth extension portion 1110 forms a linearportion 1113, and the linear portion 1113 is curved towards a centralupper surface 1103 of the rotor teeth 1100 and the core center. Thecentral upper surface 1103 of the rotor teeth 1100 has an arc angle (A1)of 60° so as to minimize cogging torque and torque ripple. As shown inFIG. 21, the height (thickness, DH) of the end of the teeth extensionportion 1110 is set to be small so as to reduce cogging torque and thetorque ripple. However, the height (DH) is preferably set to be 0.3 mmor less than, as a minimum value for processing.

FIGS. 22 and 23 are graphs showing cogging torque and torque rippleaccording to a distance (DW) between teeth extension portions 1110 ofneighboring rotor teeth 1100 of FIG. 21. Referring to FIG. 22, coggingtorque is minimum (refer to oblique line) when the distance (DW) betweenteeth extension portions 1110 of neighboring rotor teeth 1100 is 1.0 mmor less than, or is in the range of 5.5 mm˜6.5 mm. As shown in FIG. 23,torque ripple is minimum when the distance (DW) is 1.0 mm or less than.And, the torque ripple is gradually increased, but is decreased when thedistance (DW) is in the range of 5.0˜6.5. Preferably, the distance (DW)between teeth extension portions of neighboring rotor teeth is 1.0 mm orless than. However, this configuration for fabricating a motor issubstantially very difficult. Therefore, the distance (DW) is set to bein the range of 5.5 mm˜6.5 mm.

According to still another embodiment of the present invention, theteeth extension portion 1110 of the rotor teeth 1100 is provided with anextension linear portion 1113 on an outer circumference thereof. Anangle between the extension linear portion 1113 and a straight line fromthe end of the teeth extension portion to the core center is in therange of 90°˜100°. As shown in FIG. 24 (A2=90° and FIG. 25 (A2=95°, theangle (A2) between the extension linear portion 1113 and a straight linefrom the end of the teeth extension portion to the core center can beset in various manners. If the angle (A2) is in the range of 90°˜100°,cogging torque and torque ripple can be minimized. The occurrence ofcogging torque or torque ripple may be influenced by a curved degree ofthe teeth extension portion 1110 from an inner diameter of the stator2000 towards the core center. That is, when the teeth extension portion1110 is formed to be parallel to the inner diameter of the stator 2000,cogging torque can be reduced due to no leakage of magnetic flux.However, in this case, it is difficult to reduce vibrations and noisedue to torque ripple. On the other hand, when the teeth extensionportion 1110 is excessively curved towards the core center, torqueripple can be reduced. However, in this case, it is difficult to preventleakage of magnetic flux and reduce cogging torque. This may result inthe occurrence of large cogging torque. In the present invention, theangle (A2) is set to be in the range of 90°˜100° for minimization ofcogging torque and torque ripple. This can minimize vibrations and noisewhen the permanent magnet motor rotates, thereby implementing a stableoperation.

First of all, a structure of a rotor of the driving motor 70 applied tothe washing machine of the present disclosure will be explained in moredetails. As the driving motor 70 of the washing machine, used is apermanent magnet motor. The rotor structure of the permanent magnetmotor is to attenuate vibration due to rotation damping and to decreasecogging torque by improving a shape of an outer circumferential surfaceof rotor teeth 1100, and to prevent separation of the rotor teeth 1100and the permanent magnet (M) due to a centrifugal force by a cut recess1150.

Hereinafter, the rotor structure of the permanent magnet motor appliedto the washing machine of the present disclosure will be explained inmore details with reference to FIGS. 18, 26 to 29. FIG. 18 is a viewshowing an inner core of the permanent magnet motor applied to thewashing machine, FIG. 26 is a planar view showing an arrangement forfabricating rotor teeth in a punching manner, FIG. 27 is a partial viewshowing a stator and a rotor of the permanent magnet motor, FIG. 28 is apartial detailed view showing a cut recess, a cut opening and an outercircumferential curvature of the rotor tooth, and FIG. 29 is a planarview showing different exemplary embodiments of the rotor tooth.

The permanent magnet motor of the present disclosure includes a stator2000 and a rotor 1000. The stator 2000 has stator teeth 2021 and statorslots 2023, and fixedly-installed as a coil is wound on the statorteeth. The rotor has rotor teeth 1100, a permanent magnet (M) and abushing 2040, is spaced from an inner circumference of the stator 2000,and rotates centering around a rotor shaft by a magnetic force. Therotor teeth 1100 consists of a teeth extension portion 1110 extendingfrom a side end of an outer circumference of the rotor teeth in acircumferential direction, a cut recess 1150 cut in a concaved mannerfrom the outer circumference of the rotor teeth toward the center of therotor shaft, and an insertion recess 1130 cut in a concaved manner in aradial direction from an inner circumference of the rotor teeth, andconfigured to insert an injection-molding material of the bushingthereinto.

Basic configurations of the stator 2000 and the rotor 1000 have beenaforementioned. Therefore, the present disclosure will be explainedmainly with the rotor teeth 1100. FIGS. 18, 26 to 29 illustrate apermanent magnet motor having a single rotor structure. However, thepermanent magnet motor may have a dual rotor structure including aninner rotor and an outer rotor. As shown in FIGS. 18 and 26, the rotorteeth 1100 is formed in an approximate trapezoid shape, and is formed ina tapered shape such that an upper surface has a predetermined curvatureand two sides have widths gradually narrowed toward the downside. Thecut recess 1150 is concavely-formed at the center of an upper surface ofthe rotor teeth 1100, and the insertion recess 1130 is concavely-formedat the center of a lower surface of the rotor teeth 1100. The teethextension portion 1110 is protruding from an upper part of the rotorteeth 1100 in left and right directions.

Firstly, the fabrication processes of the rotor teeth 1100 will beexplained. As shown in FIG. 26, a plurality of the rotor teeth 1100 aredisposed to face each other in a zigzag direction, and then are punched.In the present disclosure, the protrusion fixing end is removed from theconventional rotor teeth, and the insertion recess 1130 is inwardlyformed to fabricate the rotor teeth 1100 in a punching manner. This mayreduce the amount of redundant parts after punching, thereby reducingwaste of components and enhancing an economic characteristic.

Referring to FIG. 27, the insertion recess 1130 includes a firstinsertion recess 1131 through which an injection-molding material of thebushing 2040 is inserted into the rotor teeth 1100, and a secondinsertion recess 1132 extending from the first insertion recess 1131 toa radial direction of the rotor shaft, and integrally-fixing the bushing2040 and the rotor teeth 1100 after hardening the injection-moldingmaterial of the bushing 2040 inserted thereinto is hardened. The firstinsertion recess 1131 serves as a path along which a liquidinjection-molding material of the busing is inserted. As shown in FIG.27, the first insertion recess 1131 is concavely formed at an inner sideof the rotor teeth 1100. The insertion recess 1130 may be formed invarious shapes, and may have any shapes to integrate the bushing 2040and the rotor teeth 1100 with each other after an injection-moldingmaterial of the bushing 2040 inserted thereinto is hardened.

Referring to FIGS. 27 and 29, the second insertion recess 1132 may beformed as a circular or oval through hole having a diameter larger thana width of the first insertion recess 1131. Alternatively, the secondinsertion recess 1132 may be formed as a polygonal through hole having awidth wider than a width of the first insertion recess 1131. Preferably,the second insertion recess 1132 is formed as a triangular through hole,so that the second insertion recess 1132 and the first insertion recess1131 entirely form a cut opening having an arrow shape. In the presentdisclosure, a protrusion fixing end formed at an inner side toward thecenter is removed from the rotor teeth 1100. This may reduce theoccurrence of inferiority due to transformation of the protrusion fixingend, may facilitate an assembly, and may prevent leakage of a magneticflux to the upper side.

Furthermore, the rotor teeth and the bushing 2040 are integrallyinjection-molded through the insertion recess 1130. This may allow therotor teeth to be simply assembled with the rotor core. As shown inFIGS. 27 and 28, the cut recess 1150 may be concaved from the center ofan upper surface of the rotor teeth 1100. This is in order to reduceinconsecutive rotations of the rotor teeth 1100, the inconsecutiverotations occurring due to a magnetic force difference between thestator slot 2023 and the stator teeth 2021 when the rotor teeth 1100spaced from the stator 2000 rotates by a magnetic flux formed by thecoil wound on the stator teeth 2021 and the permanent magnet. Therefore,the cut recess 1150 is preferably concaved from an upper surface of therotor teeth 1100.

As shown in FIGS. 29 b and 29 c, the cut recess 1150 is cut in a taperedshape that a width becomes narrow toward the center from an uppersurface of the rotor teeth 1100, thereby having a controlled distancefrom an inner circumferential surface of the stator 2000. This mayminimize the occurrence of inconsecutive points of a rotational force.The rotor teeth 1100 may further include a cut opening 1160 extendingfrom the cut hole 1150 toward the center, and forming a flux barrier asan injection-molding material of the bushing is filled therein.Preferably, the cut opening 1160 which forms a flux barrier is formed ina circular or oval shape having a diameter larger than a width of thecut recess 1150, so as to prevent leakage of a magnetic flux of thepermanent magnet (M) positioned between the rotor teeth 1100 and therotor teeth 1100.

A magnetic flux is formed on the rotor teeth 1100 by a magnetic flux ofthe permanent magnet (M) positioned between the rotor teeth 1100 and therotor teeth 1100. And, the rotor teeth 1100 has a rotational force by amagnetic flux formed by the coil wound on the stator teeth 2021 and thepermanent magnet (M). In order to maximize a magnetic force between therotor teeth 1100 and the stator teeth 2021, leakage of a magnetic fluxof the permanent magnet (M) is preferably minimized. Therefore, anadditional flux barrier is generally installed at the teeth extensionportion 1110 of the rotor teeth 1100.

However, in the present disclosure, the cut opening 1160 is additionallyformed at a point extending from the cut recess 1150 of the rotor teeth1100, and serves as a flux barrier. This may simplify the entirestructure and facilitate the fabrications. Preferably, the cut opening1160 serving as a flux barrier is formed to have a width greater thanthat of the cut recess 1150 in order to prevent leakage of a magneticflux. As shown in FIG. 29, the cut opening 1160 may be formed in variousshapes.

As shown in FIG. 28, the cut recess 1150 and the cut opening 1160 of therotor teeth 1100 are filled with an injection-molding material 2043 ofthe bushing 2040. This may prevent separation of the rotor teeth 1100from the rotor core, and may reduce cogging torque as aforementioned. Asshown in FIGS. 27 and 28, since a space between the teeth extensionportion 1110 of the rotor teeth 1100 and the permanent magnet (M) isfilled with the injection-molding material 2043 of the bushing 2040, therotor teeth 1100 and the permanent magnet (M) are integrally fixed toeach other. This may prevent separation of the rotor teeth 1100 from therotor core due to a centrifugal force.

Referring to FIG. 27, an outer circumferential end of the rotor teeth1100 has a curvature larger than that of the annular rotor. This maychange a spacing distance between an outer circumferential surface ofthe rotor teeth 1100 and an inner circumferential surface of the stator2000. More concretely, a spacing distance between an outer circumferenceof the rotor teeth 1100 and an inner circumference of the stator 2000 iscontrolled by setting a curvature of the teeth extension portion 1110 tobe different from that of a curvature of the rotor core. This mayattenuate vibrations by rotation damping, and may reduce cogging torque.Furthermore, a spacing distance (H1) between two ends of the teethextension portion 1110 and an inner circumferential surface of thestator 2000 is preferably formed to be longer than a spacing distance(H2) between the end of the cut recess 1150 and the innercircumferential surface of the stator 2000. As shown in FIG. 27, whenthe rotor 1000 approaches to the stator teeth 2021 while rotating alongthe outer circumferential surface of the rotor teeth 1100, the spacingdistance decreases to H2′ from H1′. As the spacing distance graduallydecreases, a magnetic force gradually increases. Furthermore, as adrastic change of a rotational force is minimized to reduce vibrations.

In the permanent magnet motor of the present disclosure, the rotor teeth1100 and the permanent magnet (M) are arranged in a ring shape, and aninjection-molding material of the bushing 2040 is filled in a spacetherebetween to be hardened. This may implement the rotor in anintegrated manner. Then, the injection-molding material is filled in thecut recess 1150 and the insertion recess 1130 of the rotor teeth 1100,and is filled in a space formed by the teeth extension portion 1110 ofthe rotor teeth 1100 and the permanent magnet (M). This may fix the coresince the rotor teeth and the permanent magnet are integrally formed soas to prevent separation due to a centrifugal force.

Before explaining a method for fabricating a dual motor stator of thedriving motor 70 applied to the washing machine of the presentdisclosure, will be explained a configuration of a dual motor stator ofthe present disclosure. Referring to FIG. 30, the dual motor stator ofthe present disclosure includes an inner stator 3100 including aplurality of inner teeth 3110 protruding toward the center in a ringshape, an inner yoke 3130 which forms a ring shape of an inner stator,and inner slots 3150 serving as spaces between the inner teeth 3110 andthe inner yoke 3130; an outer stator 3200 including a plurality of outerteeth 3210 protruding in a radial direction in a ring shape, an outeryoke 3230 contacting an outer circumferential surface of the inner yoke3130 and forming a ring shape of the outer stator, and outer slots 3250serving as spaces between the outer teeth 3210 and the outer yoke 3230;and an insulator 3300 installed between an outer circumferential surfaceof the inner yoke 3130 and an inner circumferential surface of the outeryoke 3230, and shielding a magnetic force.

As shown in FIG. 30, the inner stator 3100 is provided therein with aninner rotor mounting portion 3500 for mounting an inner rotor, and isprovided with a rotor shaft at the center thereof. The inner stator 3100includes an inner yoke 3130 formed in an annular belt. A plurality ofthe inner teeth 3110 are protruding, toward the center, from an innercircumferential surface of the inner yoke 3130 of the inner stator 3100with a predetermined gap therebetween. The inner teeth 3110 is providedwith an inner teeth extension portion 3111 extending from right and leftsides thereof, so that a plurality of the inner slots 3150, spacesformed by the inner teeth 3110, the inner teeth extension portions 3111and the inner yoke 3130 may be repeatedly implemented with apredetermined gap therebetween.

As shown in FIG. 30, the outer stator 3200 is formed in a ring shapewhich encompasses an outer circumferential surface of the inner yoke3110 of the inner yoke 3100, and is provided with an outer rotor mountedon an outer surface thereof. Although not shown, the outer rotorimplements a dual rotor system together with the inner rotor as itrotates. The outer stator 3200 includes an outer yoke 3230 formed in anannular belt. As an outer circumferential surface of the inner yoke 3130contacts an inner circumferential surface of the outer yoke 3230, anintegrated dual motor stator is implemented. On an outer circumferentialsurface of the outer yoke 3230 of the outer stator 3200, the outer teeth3210 are protruding in a radial direction with a predetermined gaptherebetween.

The outer teeth 3210 is provided with an outer teeth extension portion3211 extending from right and left sides thereof, so that a plurality ofthe outer slots 3250, spaces formed by the outer teeth 3210, the outerteeth extension portions 3211 and the outer yoke 3230 may be repeatedlyimplemented with a predetermined gap therebetween. The insulator 3300may be installed between an outer circumferential surface of the inneryoke 3130 and an outer circumferential surface of the outer yoke 3230fixedly-coupled to each other in a facing manner with a gaptherebetween. In order to shield an electromagnetic force, the inneryoke and the outer yoke are coupled to each other with a gaptherebetween, and an insulating member is preferably inserted to the gaptherebetween.

Due to the insulator 3300, a magnetic force between the inner motor andthe outer motor is not transmitted. This may implement a dual motorsystem where the inner motor and the outer motor independently operate.The insulator 3300 may be implemented as a member serving as a fluxbarrier which shields a magnetic force. Preferably, the insulator 3300is formed of a PBT-based plastic material. With reference to FIG. 30,will be explained the dual motor stator of the present disclosure, and amethod for efficiently implementing a proper torque by differentlysetting lengths of the outer teeth 3210 and the inner teeth 3220 fromeach other.

Generally, a coil wound on teeth generates a rotational force incorrespondence to a permanent magnet of the rotor. Here, the rotationalforce is proportional to a magnetic force of the permanent magnet, andthe number of windings of the coil. The more increased the number ofwindings of the coil is, the more increased the rotational force(torque) of the rotor is. According to still another embodiment of thepresent disclosure, as shown in FIG. 30, the dual motor stator is formedsuch that a length of the inner teeth 3220 is longer than that of theouter teeth 3210. As the length of the inner teeth 3220 is longer thanthat of the outer teeth 3210, the number of windings of the coil woundon the inner teeth 3220 is larger than that of the coil wound on theouter teeth 3210.

Since the number of windings of the coil wound on the inner teeth 3220is larger than that of the coil wound on the outer teeth 3210, arotational force (torque) of the inner rotor is greater than that of theouter rotor. In the dual drum washing machine of the present disclosure,the inner rotor is connected to an outer shaft to rotate a main drum,and the outer rotor is connected to an inner shaft to rotate a sub drum.Here, the inner rotor of a high torque rotates the main drum, and theouter rotor of a low torque rotates the sub drum. More concretely, inthe dual drum washing machine of the present disclosure, the main drumrequiring a high torque receives a high torque by the inner teeth 3220which receives a high rotational force due to its longer length, and thesub drum requiring a low torque receives a low torque by the outer teeth3210 which receives a low rotational force due to its shorter length.Under this configuration, torques may be effectively applied to the maindrum and the sub drum.

Hereinafter, a method for fabricating the dual motor stator according tothe present disclosure will be explained in more details with referenceto FIGS. 30 to 32. The conventional dual motor stator is fabricated in apunching manner through one integrated inner stator and outer stator.This may cause redundant parts after punching corresponding to the innerslot and redundant parts after punching corresponding to the outer slotto occur. Furthermore, in the conventional method for fabricating a dualmotor stator, a dual motor stator of a preset size and shape is punchedby integrating the inner stator and the outer stator with each other. Asa result, there is a problem that a size and a shape of the dual motorstator cannot be changed. The redundant parts after punching result inwastes of the components and lowering of an economic aspect.Accordingly, the present disclosure proposes a method for fabricating adual motor stator capable of minimizing the amount of redundant partsafter punching and having various shapes and sizes.

The method for fabricating a dual motor stator according to the presentdisclosure will be explained. As shown in FIGS. 30 to 32, the innerstator 3100 and the outer stator 3200 are individually fabricated in apunching manner. Then, the inner stator 3100 is formed in a ring shapesuch that the inner yoke 3130 is toward the outside, and the inner teeth3110 are toward the center. Then, the outer stator 3200 is wound on anouter circumference of the inner stator 3100 in a ring shape such thatthe outer yoke 3230 is toward the center, and the outer teeth 3210 istoward the outside. The inner stator 3100 and the outer stator 3200integrated with each other operate as stators positioned at the insideand the outside. An inner rotor 50 is disposed at the inside, and anouter rotor is disposed at the outside.

A method for fabricating the inner stator 3100 and the outer stator 3200will be explained. A pair of inner stators 3100 are fabricated in apunching manner in a state that the inner teeth 3110 are disposed to beengaged with each other in a lengthwise direction. And, a pair of outerstators 3200 are fabricated in a punching manner in a state that theouter teeth 3210 are disposed to be engaged with each other in alengthwise direction. This may minimize the amount of redundant partsafter punching (B) in the inner stators 3100 and the outer stators 3200,thereby minimizing the loss of components.

Referring to FIG. 31, the processes for fabricating the inner stator3100 will be explained. The inner stator 3100 may be fabricated as astraight-line type member extending in a lengthwise direction. A pair ofthe inner stators 3100 are disposed to face the reciprocal inner teeth3110, and the inner teeth 3110 are inserted into the inner slots 3150.This may minimize the amount of redundant parts after punching (B) whenfabricating the inner stator in a punching manner. As the amount ofredundant parts after punching (B) is minimized, wastes of thecomponents may be reduced and an economic aspect may be enhanced.

As shown in FIG. 32, the outer stator 3200 is fabricated in the samemanner as the inner stator 3100 of FIG. 31. As the amount of redundantparts after punching (B) is minimized, wastes of the components may bereduced and an economic aspect may be enhanced. The dual motor stator ofthe present disclosure is fabricated by the inner stator 3100 and theouter stator 3200. Firstly, the inner stator 3100 straightly-extendingin a lengthwise direction is cut by a predetermined length, and theouter stator 3200 is also cut by a predetermined length. As a result,the dual motor stator of a preset size is fabricated.

Referring to FIG. 30, the inner stator 3100 extending in a lengthwisedirection and cut by a predetermined size is implemented in a ring shapeas one end and another end thereof are connected to each other. And, theouter stator 3200 extending in a lengthwise direction and cut by apredetermined size is wound on an outer circumference of the innerstator 3100 in a ring shape. An outer circumferential surface of theinner stator 3100 and an inner circumferential surface of the outerstator 3200 are coupled to each other with a spacing distancetherebetween due to an insulating distance as the inner yoke 3130 andthe outer yoke 3230 face each other.

As shown in FIG. 32, in this integrally-assembled dual motor stator, theinner teeth 3110 of the inner stator 3100 are protruding toward thecenter to drive the inner rotor. And, the outer teeth 3210 of the outercore 3200 are protruding toward the outside in a radial direction todrive the outer rotor. The inner yoke 3130 and the outer yoke 3230 maybe coupled to each other in a state that the insulator 3300 whichshields a magnetic force is disposed therebetween. As aforementioned,the insulator 3300 is formed of a PBT-based plastic material such thatthe inner rotor and the outer rotor operate independently from eachother.

Hereinafter, description will be given of a stator structure inaccordance with another exemplary embodiment with reference to theaccompanying drawings. An inner stator 471 a may have a ring shape, andan outer stator 471 b of a ring shape may be disposed outside the innerstator 471 a. That is, the outer stator 471 b may surround an outercircumferential portion of the inner stator 471 a. Each of the innerstator 471 a and the outer stator 471 b may include a plurality ofarticulated bobbins connected together into a ring shape, a plurality ofteeth inserted into the articulated bobbins, respectively, and a toothring for annularly connecting end portions of the plurality of teeth.

FIG. 33 is an exemplary view of the inner stator 471 a of the stators.Without the present disclosure being limited thereto, the outer statormay be formed along the outer circumferential portion of the innerstator of FIG. 33 according to the same method. Also, a wound coil hasbeen omitted from FIG. 33 for helping understanding. As shown in FIG.33, the inner stator 471 a may include a plurality of articulatedbobbins 4110 connected into a ring shape, and a plurality of inner teeth4120 inserted into the plurality of bobbins, respectively. The innerstator 471 a may further include a tooth ring 4130 for connecting innerend portions of the plurality of inner teeth 4120 into a ring shape, andan inner yoke 4140 for connecting outer end portions thereof. Similar tothe inner stator 471 a, the outer stator 471 b may also include aplurality of articulated bobbins connected into a ring shape, aplurality of outer teeth inserted into the plurality of articulatedbobbins, respectively, a tooth ring for connecting outer end portions ofthe plurality of outer teeth into a ring shape, and an outer yoke forconnecting inner end portions thereof. A flux barrier for shielding amagnetic force may be disposed between the inner yoke and the outeryoke. Typically, the inner yoke and the outer yoke are preferablyconnected to each other with a spaced distance therebetween in order toshield an electromagnetic force. Therefore, the use of the flux barriermay prevent movement of the magnetic force between the inner stator andthe outer stator, which may result in implementation of a dual motorsystem in which inner rotor and outer rotor can independently workwithout interference with each other.

In the meantime, when a current is applied to a coil wound on a stator(inner and outer stators), a rotor is rotated by a magnetic fieldgenerated by the applied current. Hence, a stator core as a magneticsubstance to form a magnetic path may be provided. That is, thisexemplary embodiment employs an inner tooth core and an outer toothcore. In FIG. 33, the inner tooth core may include a plurality of innerteeth having a ring shape and protruding toward the center. Here, FIG.33 shows one exemplary embodiment employing each tooth consisting of aplurality of segment type teeth. Those segment type teeth are stacked toform one inner tooth 4120. Each segment type tooth may include extendingportions 4121 extending from an end thereof to both left and rightsides.

FIG. 34 shows a process of stacking segment type teeth constructing thestator core. As shown in FIG. 34, teeth (the upper part of FIG. 34) inthe form of a flat plate are punched out (the middle part of FIG. 34)and stacked by one another (the lower part of FIG. 34), thereby formingone inner tooth or outer tooth. The stator teeth of the segment typeteeth (the lower part of FIG. 34) stacked in FIG. 34 form a stator core.Each segment type tooth may include extending portions extending from anend thereof to both left and right sides. The stacked teeth, as shown inthe lower part of FIG. 34, are inserted into the articulated bobbin4110. FIG. 35 shows an articulated bobbin. As shown in FIG. 35A, thearticulated bobbin 4110 may include a body part 4111 having a receivingportion 4111 c in which the corresponding tooth is inserted, andarticulated parts 4112 formed at both side surfaces of the body part4111 to be bent.

The receiving portion 4111 c indicates a space formed within the bodypart 4111. Both end portions 4111 a and 4111 b of the body part 4111 areopen. Therefore, the receiving portion 4111 c may be defined as a spacehaving both sides open. The inner tooth or outer tooth may be receivedin the receiving portion 4111 c. In FIG. 33, the segment type innertooth 4120 is received in the receiving portion 4111 c. Here, the innertooth 4120 is inserted into a lower end portion 4111 a of the body part4111, and the extending portions 4121 of the inner tooth are located atthe lower end portion 4111 a of the body part 4111.

The articulated bobbin 4110 may be provided in plurality. FIG. 35B showsa state that a plurality of articulated bobbins are connected together.The articulated parts 4112 of the bobbin may be interconnected to thearticulated parts 4112 of the adjacent bobbins. That is, the articulatedparts 4112 may be bent with respect to the body part 4111, and capableof being coupled to the articulated parts of other bobbins. The couplingbetween the adjacent articulated parts may be implemented by well-knowncoupling methods such as hinge-coupling. After inserting the teeth intothe articulated bobbins 4110 connected together as shown in FIG. 35B,each of the articulated bobbin 4110 may be wound by a coil. That is, thecoil may be wound around the body part 4111 of the articulated bobbin4110.

The connected form of the articulated bobbins shown in FIG. 35B may beallowed for automatic winding. In the related art, teeth were receivedin an annular insulator and a coil was wound on the insulator.Accordingly, there was no way but winding the coil inside the annularinsulator using a needle. This caused a concentrated winding that thecoil wound was concentrated on a specific portion. However, upon use ofthe articulated bobbins, which can be bent, as shown in FIG. 35B,winding may be allowed by use of an automatic winding machine. Thisallows an aligned winding that a coil is wound on a circumference of thebody part with being well-aligned. This can improve a winding spacefactor and thereby enhance performance of a driving motor. In addition,when two stators are employed for driving two independent rotors asshown in the present disclosure, the enhancement of the performance ofthe driving motor by the improvement of the winding space factor maybring an opportunity for size reduction of the driving motor.

Meanwhile, the articulated bobbins, in which teeth are inserted and onwhich the coil is wound, are fixed onto an annular yoke. FIG. 36 showsthe inner yoke 4140 having the annular shape. The articulated bobbinsare connected to an inner circumferential surface of the inner yoke ofFIG. 36. The inner yoke 4140 may include a plurality of connection slits4141 formed along the inner circumferential surface thereof. Protrusionsmay be formed at ends of the inner teeth or ends of the articulatedbobbins so as to be inserted into the connection slits 4141. FIG. 33shows the articulated bobbins 4110 connected to the inner yoke 4140. Asaforementioned, the outer stator may be formed in the similar manner.That is, the outer yoke of the annular shape is provided and thearticulated bobbins are connected to an outer circumferential surface ofthe outer yoke.

The tooth ring may be press-fit in another end of the articulatedbobbin, opposite to the end connected with the inner yoke. FIG. 37 showsthe tooth ring 4130 used in the inner stator. The tooth ring may have acylindrical shape and include a plurality of protrusions 4131 formedalong an outer circumferential subsurface thereof. The protrusions 4131may be formed to press-fit the tooth ring, and accordingly bepress-fitted between the articulated bobbins or in slits formed at theinner teeth. The outer stator may be formed similarly, asaforementioned. That is, a plurality of protrusions are formed along aninner circumferential surface of the cylindrical tooth ring, thus to bepress-fitted between the articulated bobbins or the like. The tooth ringmay reduce cogging torque and prevent lowering of an output of thedriving motor. That is, the cogging torque is generated during rotationof the rotor due to discontinuity of magnetic field, which is caused byan interval between teeth. Such discontinuity may be reduced by virtueof the tooth ring, thereby reducing the cogging torque and preventingthe lowering of the output of the driving motor.

With the plurality of articulated bobbins being mounted between the yokeand the tooth ring, the plurality of articulated bobbins can bemaintained in a stable mounted state. In FIG. 33, a space may be definedbetween the body part of the articulated bobbin, which is fixed betweenthe inner yoke and the tooth ring, and a body part of an adjacentarticulated bobbin. The space may be referred to as an inner slot 4150.On the inner slot 4150 may be located the coil wound. An outer slot maybe formed similar to this, and a coil wound may be located on the outerslot.

FIG. 38 shows another exemplary embodiment of a stator according to thisspecification, which shows that the teeth are integrally formed with anarticulated yoke for connecting end portions of the teeth. In theexemplary embodiment of FIG. 38, overlapped parts with the exemplaryembodiment of FIG. 33 will not be repeatedly explained herebelow. FIG.38 exemplarily shows an inner stator 471 a of stators. Without thepresent disclosure being limited thereto, an outer stator may be formedalong an outer circumferential portion of the inner stator according tothe same way. Also, for easy understanding, a wound coil is omitted fromFIG. 38.

As shown in FIG. 38, the inner stator 471 a may include a plurality ofarticulated bobbins 4110 connected into a ring shape, and inner teeth4120 inserted into the plurality of articulated bobbins, respectively.The inner stator 471 a may further include a tooth ring 4130 forconnecting inner end portions of the plurality of inner teeth into aring shape. However, a separate inner yoke may not be needed because theinner teeth are integrally formed with the articulated yoke 4122. InFIG. 38, an inner tooth core may include a plurality of inner teethintegrally formed with the articulated yoke 4122 and protruding from thearticulated yoke 4122. This may be referred to as an integral tooth. Theplurality of integral teeth may be stacked to form one inner tooth 4120.This exemplary embodiment illustrates that the integral tooth does nothave extending portions extending from an end thereof to both left andright sides. This is because the integral tooth is inserted from anupper portion 4111 b of the body part of the articulated bobbin 4110when being inserted into the articulated bobbin 4110.

FIG. 39 shows a process of stacking the integral teeth constructing thestator core. As shown in FIG. 39, teeth in the form of a flat plate (theupper part of FIG. 39) are punched out (the middle part of FIG. 39) andstacked by one another (the lower part of FIG. 39), thereby forming oneinner tooth or outer tooth. The stacked integral teeth (the lower partof FIG. 39) thus form the stator core. Here, wedge-shaped recesses 4125may be formed at the articulated yoke 4122. The articulated yoke has tobe bent into a ring shape after the integral teeth are inserted into thearticulated bobbins. Hence, the wedge-shaped recesses 4125 may form bentportions where the articulated yoke can be bent into the ring shape. Thewedge-shaped recesses 4125 may thusly be formed in the direction thatthe articulated yoke is bent. That is, FIG. 39 shows the process offorming the inner teeth, so the wedge-shaped recesses 4125 may berecessed into an inner surface of the articulated yoke, from which theteeth protrude. However, when an outer tooth is formed, the wedge-shapedrecess may be recessed into an outer surface of the articulated yoke.

This exemplary embodiment also allows the tooth ring 4130 to bepress-fitted. That is, the tooth ring may be press-fitted in anotherside of the articulated bobbins opposite to the articulated yoke beinglocated. Therefore, the articulated yoke may be bent into the ringshape, and the plurality of articulated bobbins may be mounted betweenthe articulated yoke of the ring shape and the tooth ring. FIG. 38 showsa space defined between the body part of the articulated bobbin, whichis fixed between the articulated yoke and the tooth ring, and a bodypart of an adjacent articulated bobbin. This space may be referred to asan inner slot 4150. On the inner slot 4150 may be located the coilwound.

FIG. 35 shows an exemplary embodiment of a method for fabricating astator of a driving motor for a washing machine. As shown in FIG. 35, amethod for fabricating a stator of a driving motor for a washing machineaccording to the one exemplary embodiment may include a bobbinconnecting step (S100) of connecting a plurality of articulated bobbinsin the form of a belt, a tooth inserting step (S200) of inserting teethinto the plurality of connected articulated bobbins, respectively, anautomatic winding step (S300) of automatically winding a coil on eachtooth-inserted articulated bobbin (S400), a yoke connecting step (S400)of connecting the coil-wound articulated bobbins into a ring shape, anda tooth ring connecting step (S500) of connecting a tooth ring of a ringshape for connecting end portions of the teeth.

The bobbin connecting step (S100) indicates a step of connecting theplurality of articulated bobbins in the form of the belt. This is toconnect the articulated bobbins as shown in FIG. 35B. The toothinserting step (S200) indicates a step of inserting the teeth into theplurality of articulated bobbins, respectively. Here, segment type teethmay first be stacked in the form of each (inner or outer) tooth as shownin the lower part of FIG. 34, to be then inserted into the articulatedbobbin. Here, in the exemplary embodiment of employing the segment typeteeth of the aforementioned embodiments, the teeth are inserted into thelower sides of the articulated bobbins. On the contrary, in theexemplary embodiment of employing the integral teeth, the teeth areinserted into the upper sides of the articulated bobbins.

The automatic winding step (S300) indicates a step of automaticallywinding a coil on each tooth-inserted articulated bobbin. Asaforementioned, since the articulated bobbins are capable of being bent,the coil can be wound using an automatic winding machine. This allowsthe coil to be wound on the articulated bobbin in an aligned state. Withthe configuration, the coil may be automatically wound on thearticulated bobbin in order to improve a winding space factor, which mayresult in enhancement of the performance of the driving motor andoptimization of the driving motor.

The yoke connecting step (S400) indicates a step of connecting thecoil-wound articulated bobbins into the ring shape. Here, when the teethare the segment type teeth, the yoke connecting step may be performed toconnect the articulated bobbins to the yoke of the ring shape. However,for the integral teeth integrally formed with the articulated yoke forconnecting the end portions of the teeth, the yoke connecting step maybe performed to bend the articulated yoke into the ring shape. The toothring connecting step (S500) indicates a step of press-fitting the toothring for connecting the end portions of the teeth into the ring shape.This, as aforementioned, can reduce the cogging torque and prevent thelowering of the output of the driving motor.

Referring to FIG. 30, an inner stator 471 a may include an inner toothcore having a plurality of inner teeth 4100, and an inner yoke 4110. Theinner yoke may have a ring shape, and serve as a base from which theinner teeth 4100 protrude toward the center. That is, the inner teethmay protrude toward the center with being fixed to the inner yoke. Theplurality of inner teeth 4100 protruding toward the center may be fixedto the inner yoke 4110 with predetermined intervals therebetween. Here,a space between the inner teeth may be referred to as an inner slot4120, which provides a space where the inner tooth core is received inan insulator 478 to be explained later and thereafter a coil is wound onthe insulator 478.

Extending portions 4115 may extend from an end of each inner tooth 4100in both left and right directions. Accordingly, a space defined by theinner teeth 4100, the extending portions 4115 of the inner teeth and theinner yoke 4110 may form the inner slot 4120. Therefore, as shown inFIG. 30, the plurality of inner slots may be repeatedly formed withpredetermined intervals along a circumference formed by the inner yoke.Similar to the inner stator, an outer stator may be formed. Referring toFIG. 41, the outer stator 471 b may include an outer tooth core having aplurality of outer teeth 200, and an outer yoke 4210.

The outer yoke 4210 may have a ring shape and serve as a base from whichthe outer teeth 420 protrude in a radial direction. That is, the outerteeth may radially protrude with being fixed to the outer yoke. Theplurality of radially-protruded outer teeth 4200 may be fixed to theouter yoke 4210 with predetermined intervals therebetween. Here, a spacebetween the outer teeth may be referred to as an outer slot 4220, whichprovides a space where the outer tooth core is received in an insulator478 to be explained later and thereafter a coil is wound on theinsulator 478. Extending portions 4215 may extend from an end of eachouter tooth 4200 in left and right directions. Accordingly, a spacedefined by the outer teeth 4200, the extending portions 4215 of theouter teeth and the outer yoke 4210 may form the outer slot 4220.Therefore, as shown in FIG. 30, the plurality of outer slots may berepeatedly formed with predetermined intervals along a circumferenceformed by the outer yoke.

Here, the inner tooth core and the outer tooth core are generally formedby punching out teeth in the form of a flat plate and stacking theteeth. Therefore, required is a configuration for fixing them andallowing a coil to be wound thereon. The insulator 478 may fix thoseinner and outer tooth cores and allow a coil to be wound on the innerand outer tooth cores. The insulator 478 has the structure of receivingthe inner tooth core and the outer tooth core, and, for example, may beformed by coupling an upper insulator and a lower insulator to face eachother. Alternatively, the insulator 478 may include an insulator caseand a cover.

FIG. 41 shows an insulator 478. The insulator 478 may include an innertooth core receiving part 4310 having inner tooth receiving portions4311 for receiving the plurality of inner teeth, and an inner yokereceiving portion 4312 for receiving the inner yoke, and an outer toothcore receiving part 4320 having outer tooth receiving portions 4321 forreceiving the plurality of outer teeth, and an outer yoke receivingportion 4322 for receiving the outer yoke. Each of the inner toothreceiving portion 4211 and the outer tooth receiving portion 4321 mayhave a partition wall protruding along an outline of a tooth forreceiving the inner tooth and the outer tooth. Accordingly, the innertooth receiving portion and the outer tooth receiving portion may formlattice-shaped spaces, respectively, for receiving the teeth by thepartition walls. Each of the inner yoke receiving portion 4312 and theouter yoke receiving portion 4322 may also have a partition wallprotruding along an outline of the annular yoke for receiving the inneryoke and the outer yoke. Accordingly, the inner yoke receiving portionand the outer yoke receiving portion may form cylindrical spaces,respectively, for receiving the yokes by the partition walls.

The insulator 478 may further include a flux barrier 4330 for shieldinga magnetic force by spacing the inner tooth core received in the innertooth core receiving part apart from the outer tooth core received inthe outer tooth core receiving portion. The flux barrier 4330 mayprotrude in a ring shape between the inner yoke receiving portion 4312and the outer yoke receiving portion 4322. That is, an outercircumferential surface of the inner yoke received in the inner yokereceiving portion and an inner circumferential surface of the outer yokereceived in the outer yoke receiving portion may be fixed to face eachother, with the flux barrier 4330 interposed therebetween. In general,to shield an electromagnetic force, the inner tooth core and the outertooth core are preferably coupled to each other with a spaced distancetherebetween. Therefore, formation of the flux barrier 4330 may preventmovement of a magnetic field between the inner stator and the outerstator, which may result in implementation of a dual motor system inwhich an inner rotor and an outer rotor can independently work withoutinterference with each other

For example, the flux barrier 4330 may protrude from at least one of theupper insulator and the lower insulator, and make the inner tooth coreand the outer tooth core spaced apart from each other as the upper andlower insulators are coupled to each other. Accordingly, the fluxbarrier 4330 may shield magnetic field interference between the innertooth core and the outer tooth core. To this end, the insulator 478 maybe formed of PBT-based plastic. In the meantime, after the inner toothcore and the outer tooth core are received in the inner tooth corereceiving part 4310 and the outer tooth core receiving part 4320, theupper insulator and the lower insulator are assembled to each other,thereby completely producing the insulator. Here, as aforementioned, theinner slots 4120 may be formed between the inner tooth receivingportions for receiving the plurality of inner teeth, and the outer slots4220 may be formed between the outer tooth receiving portions forreceiving the plurality of outer teeth.

A wound coil may be located in the inner slot and the outer slot,respectively. That is, when the coil is wound based on the inner toothreceiving portions for receiving the inner teeth and the outer toothreceiving portions for receiving the outer teeth, the wound coil may belocated in the inner slots and the outer slots. Therefore, the innerstator may be formed by receiving the inner tooth core in the insulatorand winding the coil on the insulator, and the outer stator may beformed by receiving the outer tooth core in the insulator and windingthe coil on the insulator. Here, a coil-wound portion of the innerstator becomes an inner winding portion, and a coil-wound portion of theouter stator becomes an outer winding portion. From the perspective ofthe configuration, the insulator may serve as a bobbin for winding coilthereon as well. Also, the flux barrier may be integrally formed withthe insulator. Accordingly, a bobbin and a flux barrier are notrequired, which may result in reduction of the entire number ofcomponents and an entire size of the driving motor. In addition, even iftwo stators for driving two independent rotors are employed, an increasein an entire size of the washing machine can be avoided.

FIG. 42 shows one exemplary embodiment of a method for fabricating astator of a driving motor for a washing machine. As shown in FIG. 42, amethod for fabricating a stator of a driving motor for a washing machineaccording to the one exemplary embodiment may include a stator coreforming step (S100) of stacking an inner tooth core having inner teethand an inner yoke, and an outer tooth core having outer teeth and anouter yoke, a stator core inserting step (S200) of inserting the innertooth core and the outer tooth core in one of an upper insulator and alower insulator, which are coupled to form an inner tooth receiving partand an outer tooth receiving part and face each other, a statorassembling step (S300) of coupling the upper insulator to the lowerinsulator, and a coil winding step (S400) of winding a coil on anoutside of inner tooth receiving portions for receiving the inner teethof the inner stator receiving part, and on an outside of outer toothreceiving portions for receiving the outer teeth of the outer statorreceiving part.

The stator core forming step (S100) indicates a step of forming theinner tooth core and the outer tooth core. As aforementioned, accordingto the method of forming the inner tooth core and the outer tooth core,teeth in the form of a flat plate are punched out and stacked. That is,the inner tooth core having the inner teeth and the inner yoke and theouter tooth core having the outer teeth and the outer yoke are stackedeach other. The stator core inserting step (S200) indicates a step ofinserting the inner tooth core and the outer tooth core stacked in thetooth core forming step (S100) into the inner stator receiving part andthe outer stator receiving part of the insulator. Here, the tooth coresmay be inserted into one of the upper insulator and the lower insulator.

In the stator core inserting step (S200), the inner tooth core and theouter tooth core are inserted with being spaced apart from each other byinterposing therebetween a flux barrier, which is formed at at least oneof the upper insulator and the lower insulator. The stator assemblingstep (S300) indicates a step of completing the assembling of theinsulator by coupling the upper insulator and the lower insulator.Accordingly, the insulator may cover the inner tooth core and the outertooth core, and serve as a bobbin on which the coil is wound in thewinding step to be explained later. The coil winding step (S400)indicates a step of winding the coil on the outside of the inner toothreceiving portions for receiving the inner teeth of the inner toothreceiving part, and the outer tooth receiving portions for receiving theouter teeth of the outer tooth receiving part. With the configuration,the assembling of the stator can be performed in an easy and simplemanner, and the insulator can serve as the bobbin as well, which mayallow for reduction of the entire number of components and an entiresize of the driving motor. Therefore, even if two stators for drivingtwo independent rotors are employed, an increase in an entire size ofthe washing machine can be avoided.

With reference to FIGS. 43 to 45, will be explained a structure of abearing housing capable of enhancing a radiating characteristic of astator of a dual motor applied to the washing machine of the presentdisclosure. Firstly, a bearing housing 6100 of the present disclosurewill be explained with reference to FIG. 43. The bearing housing 6100 isprovided with a bearing shaft hole 6140 for penetrating a rotor shaft ofa stator 2000 therethrough, and is concentrically coupled to the stator2000 in a covering manner. The stator 2000 is provided with a housingmounting rib 2510 of a ring shape protruding from a yoke 2500 in anaxial direction. Preferably, a diameter of the housing mounting rib 2510is formed to be equal to or a little larger than a diameter of a body6110 of the bearing housing. More concretely, the bearing housing 6100is assembled to the stator 2000 as the body 6110 is insertion-fixed toan inner circumferential surface of the housing mounting ribs 2510.Here, the bearing housing 6100 is fitted into the stator 2000 such thata stator coupling opening 6130 and a housing coupling opening 2300 arealigned with each other.

The stator 2000 is provided with outer teeth 2100 protruding from anouter circumference in a radial direction. Although not shown, an outerrotor is mounted to an outer circumference of the outer teeth 2100 witha gap therebetween, and rotates by a magnetic force. The stator 2000 isprovided with outer teeth 2100 protruding from an inner circumferencetoward the center. Although not shown, an inner rotor is mounted to aninner circumference of the inner teeth 2200 with a gap therebetween, androtates by a magnetic force.

As shown in FIG. 43, since the bearing housing 6100 is fixedly-coupledto the yoke 2500 of the stator 2000, the bearing housing 6100 completelycovers the inner rotor. A coil 2220 formed of a conductive such ascopper is wound on a winding portion formed on an outer circumferentialsurface of a core 2210 of the inner teeth 2200. When a current isapplied to the coil 2220, the current reacts with a permanent magnet ofthe rotor to rotate the rotor. By the applied current, the coil 2220 maygenerate heat of a high temperature. This heat of a high temperature maycause the coil 2220 to be cut or to mal-operate. Therefore, it isrequired to radiate the heat. Furthermore, the heat generated from theinner rotor covered by the bearing housing 6100 is not easily radiatedto the outside. This may damage a wire wound on the inner teeth 2200, orcause a mal-operation. Accordingly, as shown in FIG. 43, the stator 2000is provided with a spacer 2510 protruding from the yoke 2500 so that thestator 2000 may be coupled to the bearing housing 6100 with a gaptherebetween.

The heat generated from the inner rotor circulates at a space betweenthe bearing housing 6100 and the yoke 2500 of the stator 2000, and isradiated to the outside without being over-heated. The spacer 2510 isformed at the yoke 2500 in plurality with a constant gap therebetween,so that the bearing housing 6100 may be sufficiently spaced from theinner rotor formed inside the stator 2000. However, the spacer 2510between the bearing housing 6100 and the inner teeth 2200 of the stator2000 merely serves to radiate heat by convection. If a spacing distancetherebetween is not sufficiently long, there are limitations inradiating heat. In order to implement radiation by conduction as well asconvection by the spacing distance, the body 6110 of the bearing housing6100 consists of a protruding portion 6111 and a concaved portion 6113.

Referring to FIGS. 43 to 45, the bearing housing 6100 having a body6110, a bearing shaft hole 6140, and a stator coupling opening 6130 isassembled to the stator 2000 having outer teeth 2100, inner teeth 2200,a yoke 2500 and a housing coupling opening 2300. Here, the body 6110 ofthe bearing housing 6100 is provided with the protruding portion 6111 ata position corresponding to the winding portion of the inner teeth 2200,and is provided with the concaved portion 6113 at a positioncorresponding to a slot (S) between the inner teeth 2200. The concavedportion 6113 may be implemented as a through hole penetratingly formedat the body 6110 of the bearing housing 6100. Since the concaved portion6113 is penetratingly formed as a space for convection, heat generatedfrom the winding portion of the inner teeth 2200 may be radiated moreeffectively. However, as shown in FIG. 45, the concaved portion 6113 maybe implemented as an outer surface of the body 6110 of the bearinghousing 6100 is curved. In this case, the body 6110 of the bearinghousing 6100 may be implemented as a curved portion integrally formedtherewith. This may maximize radiation due to conduction of theprotruding portion 6111.

The concaved portion 6113 of the body 6110 of the bearing housing isformed as a space (F) for circulating heat generated from the windingportion of the inner teeth 2200 by convection. And, the protrudingportion 6111 of the body 6110 of the bearing housing is formed as aconducting portion for radiating heat generated from the winding portionof the inner teeth 6110 to the outside by conduction. The protrudingportion 6111 of the body 6110 of the bearing housing is spaced from thecoil 2220 wound on the winding portion of the inner teeth by apredetermined insulating distance (D). This insulating distance has onlyto have a length long enough to prevent a current of the coil 2220 fromflowing to the bearing housing 6100 formed of a metallic material.Preferably, the insulating distance is approximately 3 mm.

Hereinafter, with reference to FIGS. 46 to 48, will be explainedstructures of a current connector and a hall sensor of the dual motoraccording to the present disclosure, and a washing machine using thesame. In the conventional dual motor system, each of a current connectorand a hall sensor connector is respectively installed on inner and outerstators. This may cause a complicated structure, and increase the numberof assembly processes, etc. In order to solve these various problems, inthe present disclosure, a current connector is integrally formed oninner and outer stators, and a hall sensor connector is also integrallyformed on inner and outer stators.

As shown in FIG. 46, the dual motor of the present disclosure includes acurrent connector 7300 having outer teeth 2100 and inner teeth 2200, andconfigured to apply power to an outer winding portion of the outer teeth2100 and an inner winding portion of the inner teeth 2200 in anintegrated manner; and a hall sensor connector 7500 configured to applypower to an outer hall sensor 7510 and an inner hall sensor 7520 in anintegrated manner. The outer winding portion has a structure that a coilis wound on the outer teeth 2100. Although not shown, a metallic coilsuch as copper having a high conductivity is wound on the outer teeth2100 a plurality of times, thereby rotating an outer rotor (not shown)positioned outside the outer teeth 2100 by forming a magnetic fluxtogether with a permanent magnet of the outer rotor. In correspondenceto the outer winding portion, the inner winding portion has a structurethat a coil is wound on the inner teeth 2200 a plurality of times,thereby rotating an inner rotor (not shown) positioned inside the innerteeth 2200.

The current connector 7300 has a structure to operate the motor byforming a magnetic flux together with a permanent magnet of the rotor,by applying a current to coils of the outer winding portion and theinner winding portion. An outer current connector and an inner currentconnector are separately installed in the conventional art, whereas theyare integrally formed as one current connector 7300 in the presentdisclosure. Preferably, the current connector 7300 is implemented as a6-pin connector where a 3-pin connector for applying a current to theouter winding portion is integrated with a 3-pin connector for applyinga current to the inner winding portion. In the conventional art, anouter current connector and an inner current connector have the samestructure, a 3-pin structure, respectively. However, in the presentdisclosure, an outer current connector and an inner current connectorare integrally formed as one current connector 7300, a 6-pin connector.

As shown in FIG. 47, the current connector 7300 supplies a current froma power unit 7100 to the outer winding portion and the inner windingportion in parallel. As a current is supplied to the outer windingportion and the inner winding portion through one current connector7300, a simple structure may be implemented, an assembly process may befacilitated, and the number of components may be reduced. As shown inFIG. 47, the current applied to the outer winding portions 2100 and theinner winding portion 2200 through the current connector 7300 isintegrally connected to one ground (GND). As a result, the outer windingportion 2100 and the inner winding portion 2200 have a parallelstructure.

The hall sensor connector 7500 serves to integrate an outer hall sensorconnector and an inner hall sensor connector which perform hall sensingfunctions with respect to the outer stator and the inner stator,respectively, as one connector. As shown in FIG. 46, the hall sensorconnector 7500 is formed as a connector of an outer hall sensor 7510 anda connector of an inner hall sensor 7520 of a hall sensor unit 7500 areintegrated with each other.

As shown in FIG. 48, it is preferable to supply a current from the powerunit 7100 to the outer hall sensor 7510 and the inner hall sensor 7520in parallel through the integrated hall sensor connector 7500, and toconnect hall sensing signals detected from the outer stator and theinner stator to the integrated hall sensor connector 7500 in parallel.As shown in FIG. 48, the current applied from the outer hall sensor 7510and the inner hall sensor 7520 is connected to one ground (GND) throughthe integrated hall sensor connector 7500 in parallel.

According to another embodiment of the present disclosure, as shown inFIG. 46, the dual motor of the present disclosure may further include anouter temperature sensor 7610 and an inner temperature sensor 7620 fordetecting temperatures of the outer stator and the inner stator,respectively. Referring to FIG. 46, the outer temperature sensor 7610and the inner temperature sensor 7620 are installed on a lower surfaceof the hall sensor unit 7500, respectively. The outer temperature sensor7610 is mounted to the outer stator, and the inner temperature sensor7620 is mounted to the inner stator. The outer temperature sensor 7610is installed to contact the outer winding portion to measure atemperature of heat generated from the outer winding portion, and theinner temperature sensor 7620 is installed to contact the inner windingportion to measure a temperature of heat generated from the innerwinding portion.

When overheat is generated from the respective stators, thesetemperature sensors 7610 and 7620 are configured to control theoperation of the dual motor by detecting the generated overheat.Referring to FIG. 48, a current from the power unit 7100 is supplied tothe outer temperature sensor 7610 and the inner temperature sensor 7620,in parallel, through the integrated hall sensor connector 7500.Preferably, signals detected from the outer temperature sensor 7610 andthe inner temperature sensor 7620 are connected to the integrated hallsensor connector 7500 in parallel. As the hall sensor connector 7500implemented as one integrated connector supplies power applied from thepower unit 7100 to the inner and outer stators in parallel. This mayimplement a simple structure and enhance an assembly characteristic. Asa result, an inferior coupling or an inferior operation due to acomplicated structure may be prevented.

Referring to FIG. 48, the hall sensor unit 7500 including the outer hallsensor 7510 and the inner hall sensor 7520, and a temperature sensorunit including the outer temperature sensor 7610 and the innertemperature sensor 7620 are connected to each other in parallel. And,the hall sensor unit and the temperature sensor unit are integrallyconnected to one ground (GND). The hall sensor connector 7500 has aparallel structure to connect the hall sensor unit 7500 and thetemperature sensor unit (7610, 7620) to each other. A simple assemblystructure by one power unit 7100 and the ground may be implemented, anda stable system may be implemented. A drum assembly method according toone embodiment of the present disclosure is applied to a washing machinecomprising a main drum and a sub drum independently driven in a tubfixed to the aforementioned body, and a driving motor having a statorand inner and outer rotors for independently driving the main drum andthe sub drum.

FIG. 8 illustrates a drum assembly method according to one embodiment ofthe present disclosure. Referring to FIG. 8, the drum assembly methodincludes fabricating a shaft-spider assembly by coupling a shaft and aspider to each other, the shaft which transmits a driving force to themain drum and the sub drum from the driving motor (S100), coupling theshaft-spider assembly to a rear side of the sub drum (S200), couplingthe sub drum to the main drum (S300), and coupling the shaft-spiderassembly to a rear side of the main drum (S400).

The above steps are performed after the main drum, the sub drum, a maindrum spider, a sub drum spider, etc. have been fabricated. For instance,for the main drum and the sub drum, a plate is rolled to have acylindrical shape, and a coupling part undergoes a seaming process.Furthermore, the end of the drum undergoes a curling process. FIG. 6illustrates a seamed coupling part 66 and a curled end part 67 of thesub drum. Preferably, the sub drum undergoes a curling process after aseaming process so that the curled end may have continuity. The maindrum spider and the sub drum spider may be fabricated in a die-castingmanner.

FIG. 3 is an exploded perspective view illustrating the main drum, thesub drum, etc. Referring to FIGS. 3 and 7, in S100, an outer shaft 81for transmitting a driving force to the main drum from the inner rotoris coupled to the main drum spider 91 (S110), an inner shaft 82 fortransmitting a driving force to the sub drum from the outer rotor iscoupled to the sub drum spider 95 (S120). The step (S110) for couplingthe outer shaft to the main drum spider is independent from the step(S120) for coupling the inner shaft to the sub drum spider. Therefore,the steps S110 and S120 may be performed in a reverse order, or may besimultaneously performed.

Then, the inner shaft 82 coupled to the sub drum spider is coupled tothe inside of the outer shaft 81 coupled to the main drum spider (S130).At the same time, a bearing (S131) and a waterproof seal (S132) areinserted into the inner shaft 82. Referring to FIG. 7, the inner shaftis coupled to the inside of the outer shaft, a bearing is forciblyinserted thereinto, and then a waterproof seal is inserted thereinto. InS200 for coupling the shaft-spider assembly to a rear side of the subdrum, the sub drum spider is coupled to a rear surface of the sub drum(sub drum back). In this case, since the sub drum spider is included inthe shaft-spider assembly, the shaft-spider assembly is coupled to thesub drum. The sub drum spider and the sub drum back may be coupled toeach other by screws or by welding.

In S300 for coupling the sub drum to the main drum, the sub drum isinserted into the inside of the main drum. In case of mounting a drumguide as shown in FIG. 2, the drum guide 55 for sealing is mounted tothe inside of the main drum before inserting the sub drum into the maindrum (S250). The drum guide may be mounted by fit-coupling a protrusionformed at a lower part of the drum guide to a recess formed on an innercircumferential surface of the main drum.

In S400 for coupling the shaft-spider assembly to a rear side of themain drum, the end of the main drum spider is coupled to the main drum.In this case, since the main drum spider is included in the shaft-spiderassembly, the shaft-spider assembly is coupled to the main drum. Themain drum spider and the main drum may be coupled to each other byscrews or by welding.

Hereinafter, will be explained a shaft structure for transmitting arotational force by connecting a driving motor to a drum of a washingmachine according to the present disclosure. FIG. 49 is a viewillustrating a washing machine having a shaft structure (A) according toanother embodiment of the present disclosure, FIGS. 50 and 51 aredetailed sectional and perspective views illustrating the shaftstructure (A), and FIG. 52 is a view illustrating a spring washer 900for attenuating vibrations in the shaft structure (A).

Another embodiment of the present disclosure will be explained withreference to FIGS. 50 to 52. The shaft structure (A) of the dual motoraccording to the present disclosure includes an outer shaft 81 of ahollow type; an inner shaft 82 inserted into the outer shaft 81; adriving motor 70 having an outer rotor 72 connected to a stator 71 andthe inner shaft 82 and rotating outside the stator 71, and having aninner rotor 73 connected to the outer shaft 81 and rotating inside thestator 71; and a spring washer 900 inserted into a connection part ofthe outer shaft 81 and the inner rotor 82. In this structure, vibrationsof the outer shaft are attenuated to prevent noise, and separation ofthe outer shaft 81 due to vibrations may be prevented.

Referring to FIG. 50, the inner shaft 82 rotates in an inserted stateinto the outer shaft 81 of a hollow type. The outer shaft 81 rotates ina connected state to the inner rotor 73, and the inner shaft 82 rotatesin a connected state to the outer rotor 72. The outer shaft 81 rapidlyrotates by receiving a rotational force of the inner rotor 73. In thiscase, vibrations and noise occur when the rotational force istransmitted. Therefore, the spring washer 900 is installed between theouter shaft 81 and the inner rotor 73 to attenuate vibrations in anaxial direction.

As shown in FIG. 50, an inner ball bearing 83 is installed between theouter shaft 81 and the inner shaft 82, so that the driving motor maydrive the outer shaft and the inner shaft, independently. An outer ballbearing 84 is provided on an outer circumference of the outer shaft 82,thereby rotating the outer shaft 82 in the shaft structure. As shown inFIGS. 50 and 51, the shaft structure may further include a stopping ring800 configured to fix the spring washer 900 at a connection part of theouter shaft 81 and the inner rotor 73. Here, the stopping ring 800 isimplemented as a C-ring. As shown in FIG. 52, the spring washer 900 isimplemented as a concave-convex member of a ring shape having aprotruding portion 910 and a concaved portion 930. As shown in FIG. 50,once the spring washer 900 is fit-coupled to an outer circumference ofthe outer shaft 81 by the concave-convex parts and is fixed by thestopping ring 800, vibrations of the outer shaft 81 in an axialdirection may be attenuated.

In order to compress the spring washer 900 in an axial direction and toimplement an elastic force by the concave-convex parts, the stoppingring 800 has to restrict an upper surface of the spring washer 900 asshown in FIG. 50. The outer shaft 81 is provided with a stopping ringrecess 81 a concaved toward the center on an outer circumferencethereof, thereby preventing separation of the spring washer 900 in anaxial direction by inserting the stopping ring 800 (C-ring) into thestopping ring recess 81 a. As shown in FIG. 51, the stopping ring 800 isformed in a partially-cut ring shape (C-ring) in order to be fit intothe stopping ring recess 81 a formed on an outer circumference of theouter shaft 81. The C-ring is fit into the stopping ring recess 81 aformed on an outer circumference of the outer shaft 81 as a cut partthereof is widened.

Referring to FIGS. 50 and 51 according to another embodiment of thepresent disclosure, an inner bushing 73 a is installed between the outershaft and the inner rotor, thereby transmitting a rotational force ofthe inner rotor 73 to the outer shaft 81. An outer bushing 72 a is alsoinstalled between the inner shaft 82 and the outer rotor 72, therebytransmitting a rotational force of the outer rotor 72 to the inner shaft82. In order to prevent vibrations and noise of the outer shaft 81 in anaxial direction, the spring washer 900 further includes a stopping ring800 installed between the inner bushing 73 a and the outer shaft 81, andconfigured to fix the spring washer 900 at a connection part of theouter shaft 81 and the inner bushing 73 a.

As shown in FIGS. 50 and 51, the spring washer 900 may be formed in anannular member which encompasses an outer circumference of the outershaft 81 on an upper surface of the inner bushing 73 a. A stopping ringrecess 81 a is concaved from an outer circumference of the outer shaft81 toward the center. The stopping ring 900 is implemented as a C-ringinserted into the stopping ring recess 81 a, and prevents separation ofthe spring washer in an axial direction by contacting an upper surfaceof the spring washer 900.

According to still another embodiment of the present disclosure, astructure to couple a serration of the inner shaft 82 to the outerbushing 72 a has a tapered shape. This may enhance a user's conveniencewhen performing the coupling process, and may enhance a coupling force.Referring to FIGS. 50 and 51, one end of the inner shaft 82 at a drivingmotor side is provided with serrations for transmitting a rotationalforce of the outer rotor to the inner shaft 82. The serrations of theinner shaft 82 and an inner circumferential surface of the inner bushing72 a are formed in a sawteeth shape, so that a rotational force istransmitted to the inner shaft 82 from the inner bushing 72 a when theyare engaged with each other.

The serrations of the inner shaft 82 are fit into sawteeth of an innercircumferential surface of the inner bushing 72 a. As shown in FIGS. 50and 51, the inner shaft 82 and the inner bushing 72 a are formed inparallel cylindrical shapes. In this case, the serrations of the innershaft 82 and the inner circumferential surface of the inner bushing 72 amay have a gap therebetween, and may have a difficulty in being coupledto each other. As a result, it may be difficult to transmit a rotationalforce to the shaft from the rotor. Although not shown, the serrations ofthe inner shaft 82 may be formed in a tapered shape. Further, the innercircumferential surface of the inner bushing 72 a may be implemented asa tapered through hole. This may allow the inner shaft 82 to beinsertion-coupled to the inner bushing 72 a with a large coupling force.And, a coupling intensity may be reinforced and an assemblycharacteristic may be enhanced.

Still another embodiment of the present invention will be explained inmore details with reference to FIGS. 52 and 53. A shaft structure for adual drum washing machine comprises an outer shaft 81 formed in a hollowtype; an inner shaft 82 inserted into the outer shaft 81; a drivingmotor having a stator 71, an outer rotor 72 connected to the inner shaft82 and rotating outside the stator 71, and an inner rotor 73 connectedto the outer shaft 81 and rotating inside the stator 71; a spring washer500 inserted into the outer shaft at a connection part of the outershaft 81 and the inner rotor 82; and an inner rotor nut 310 configuredto forcibly fix the inner rotor after the spring washer 500 has beeninsertion-coupled to the outer shaft. Under this configuration,vibrations of the outer shaft can be attenuated to prevent noise, andentangled state releasing due to vibration can be prevented.

Referring to FIG. 53, the inner shaft 82 is inserted into the outershaft 81 for rotation. The outer shaft 81 is connected to the innerrotor 73, and the inner shaft 82 is connected to the outer rotor 72 forrotation. The outer shaft 81 rotates at a high speed by receiving arotational force of the inner rotor 73. When the rotational force istransmitted, vibrations and noise occur. To prevent vibrations in anaxial direction, the spring washer 500 is disposed between the outershaft 81 and the inner rotor 73.

Referring to FIG. 53, an inner ball bearing 83 is installed between theouter shaft 72 and the inner shaft 73, so that the driving motor canindependently drive the outer shaft and the inner shaft. An outer ballbearing 84 is provided on the outer circumference of the outer shaft 82,which allows rotation of the outer shaft 82 in the shaft structure forthe washing machine. As shown in FIG. 53, the shaft structure of thepresent invention may further comprise an inner rotor nut 310 configuredto fix the spring washer 500 at a connection part of the outer shaft 81and the inner rotor 73.

As shown in FIG. 52, the spring washer 500 is implemented in the form ofan annular concave-convex member having a protrusion part 510 and aconcaved part 530. Referring to FIG. 53, when the spring washer 500 isfittedly-inserted into the outer circumference of the outer shaft 81 bythe concave-convex part thus to be fixed by the inner rotor nut 310,vibrations of the outer shaft 81 in an axial direction can beattenuated. In order to provide an elastic force due to theconcave-convex part by compressing the spring washer 500 in an axialdirection, as shown in FIG. 53, the inner rotor nut 310 has to bescrew-coupled to an outer circumferential surface of the end of theouter shaft 81 for restriction of an upper surface of the spring washer500.

The shaft structure of the present invention may further comprise aplain washer 501 insertion-coupled to part between the inner rotor 73and the spring washer 500 on the outer circumference of the outer shaft81. As shown in FIG. 53, the plain washer is forcibly insertion-coupledbetween the upper surface of the spring washer 500 and the upper surfaceof the inner rotor 73. The inner rotor nut 310 serves to forcibly fixthe spring washer 500 on the outer circumference of the outer shaft 81.Since the inner rotor 73 and the spring washer 500 do not directly comein contact with each other due to the plain washer 501, a coupling forcetherebetween can be enhanced and vibrations can be reduced. This canprevent entangled state releasing.

As shown in FIG. 53, a male screw portion 81 a is formed on the outercircumference of the outer shaft 81, and a female screw portion 310 a isformed on the inner circumference of the inner rotor nut 310. As themale screw portion 81 a and the female screw portion 310 a arescrew-coupled to each other, the spring washer 500 can be prevented fromdeviating in an axial direction.

According to another embodiment shown in FIGS. 52 and 53, an innerbushing 73 a is installed between the outer shaft and the inner rotor,so that a rotation force of the inner rotor 73 can be transferred to theouter shaft 81. An outer bushing 72 a is installed between the innershaft 82 and the outer rotor 72, so that a rotation force of the outerrotor 72 can be transferred to the inner shaft 82. In order to preventvibrations and noise of the outer shaft 81 in an axial direction, thespring washer 500 is installed at a connection part of the inner bushing73 a and the outer shaft 81. Accordingly, the present invention furthercomprises 310 the inner rotor nut 310 configured to fix the springwasher 500 at a connection part of the outer shaft 81 and the innerbushing 73 a.

As shown in FIGS. 52 and 53, the spring washer 500 is formed in anannular member covering the outer circumference of the outer shaft 81 onan upper surface of the inner bushing 73 a. The plain washer 501 may beprovided between the inner bushing 73 a and the spring washer 500. Thiscan enhance a coupling force of the inner bushing 73 a and reducevibrations, thereby preventing entangled state releasing.

Hereinafter, with reference to FIGS. 54 to 56, will be explained astructure to enhance an assembly characteristic between a bearinghousing and a stator in a dual motor applied to a washing machineaccording to the present disclosure. Firstly, an assembly structure ofthe present disclosure will be explained with reference to FIG. 54. Abearing housing 6100 is provided with a bearing shaft hole 6140 forpenetrating a rotor shaft of a stator 2000 therethrough, and isconcentrically coupled to the stator 2000 in a covering manner.

The present disclosure may be applied to a dual motor system as well asa single motor system. FIG. 54 illustrates that the bearing housing 6100and the stator 2000 are assembled to each other in a dual motor systemaccording to the present disclosure. Hereinafter, the descriptions willbe explained with reference to FIG. 54. The present disclosure providesa structure to enhance an assembly characteristic between the bearinghousing and the stator of a dual motor, and a washing machine having thestructure. In the present disclosure, the bearing housing 6100 having ahousing body 6110, a bearing shaft hole 6140 and a stator couplingopening 6130 is assembled to the stator 2000 having outer teeth 2100,inner teeth 2200, a yoke 2500 and a housing coupling opening 2300. Thestator coupling opening 6130 includes a fitting protrusion 6130 a, andthe housing coupling opening 2300 includes a fitting recess 2300 a. Forthe assembly, the fitting protrusion 6130 a is inserted into the fittingrecess 2300 a.

The stator 2000 is provided with a water blocking mounting rib 2700 of aring shape protruding from the yoke 2500 in an axial direction.Preferably, the water blocking mounting rib 2700 has a diameter equal toor a little larger than a diameter of the body 6110 of the bearinghousing. More concretely, the body 6110 of the bearing housing 6100 isinsertion-fixed to an inner circumferential surface of the waterblocking mounting rib 2510. Here, the stator coupling opening 6130 andthe housing coupling opening 2300 are aligned with each other. For thealignment, the fitting protrusion 6130 a of the stator coupling opening6130 is inserted into the fitting recess 2300 a of the housing couplingopening 2300. The stator coupling opening 6130 of the bearing housing6100 is provided with the fitting protrusion 6130 a rather than thefitting recess. Since the fitting recess 6130 a is integrally protrudingfrom the bearing housing 2000, it has to be implemented as a metallicmember having a high intensity.

The stator 2000 is a stator applied to a dual motor including an innerrotor and an outer rotor. The stator 2000 is provided with the outerteeth 2100 protruding from an outer circumference in a radial direction.Although not shown, an outer rotor is mounted on an outer circumferenceof the stator with a distance from the outer teeth 2100, and rotates bya magnetic force. The stator 2000 is provided with the inner teeth 2200protruding from an inner circumference toward the center. Although notshown, an inner rotor is mounted on an inner circumference of the statorwith a distance from the inner teeth 2200, and rotates by a magneticforce. As shown in FIG. 54, the bearing housing 6100 is coupled to thestator 2000 by being fixed to the yoke 2500 of the stator 2000.Accordingly, the inner rotor is in a completely covered state. Heat of ahigh temperature generated from the inner rotor is not easily radiatedto the outside. This may damage a coil wound on the inner teeth 2200, orcause a mal-operation.

Accordingly, as shown in FIGS. 54 and 56, the stator 2000 is providedwith a spacer 2510 protruding from the yoke 2500 so that the stator 2000may be coupled to the bearing housing 6100 with a gap therebetween. Theheat generated from the inner rotor circulates at a space between thebearing housing 6100 and the yoke 2500 of the stator 2000, and isradiated to the outside without being over-heated. The spacer 2510 isformed at the yoke 2500 in plurality with a constant gap therebetween,so that the bearing housing 6100 may be sufficiently spaced from theinner rotor formed inside the stator 2000. Hereinafter, shapes andstructures of the stator coupling opening 6130 and the housing couplingopening 2300, and coupling therebetween will be explained with referenceto FIGS. 55 and 56.

The stator coupling opening 6130 and the housing coupling opening 2300are provided with coupling openings 6130 b and 2300 b communicated witheach other when the bearing housing 6100 and the stator 2000 areassembled to each other. In a state that the fitting protrusion 6130 ahas been insertion-fixed to the fitting recess 2300 a, the bearinghousing 6100 and the stator 2000 are assembled to each other by screwsthrough the coupling openings 6130 b and 2300 b. As aforementioned, thebody 6110 of the bearing housing 6100 is insertion-fixed to the waterblocking mounting rib 2700 of the stator 2000. In this case, it isdifficult to align the coupling openings 6130 b and 2300 b to each otherfor communications. Accordingly, the fitting protrusion 6130 a and thefitting recess 2300 a may be coupled to each other for alignments.

In the conventional art, the stator 2000 is provided with a fittingprotrusion, and the bearing housing 6100 is provided with a fittingrecess for alignments. However, in a case that the fitting protrusion ofthe stator 2000 is formed of a plastic material, the fitting protrusionmay be damaged, e.g., it may be broken, bent, etc. This may cause adifficulty in aligning the coupling opening 6130 b of the bearinghousing 6100 and the coupling opening 2300 b of the stator 2000 to eachother for communications. In order to solve these problems, in thepresent disclosure, the bearing housing 6100 formed of a metallicmaterial having a high intensity is provided with the fitting protrusion6130 b, and the stator 2000 formed of a plastic material is providedwith the fitting recess 2300 b. This may solve difficult assemblyprocesses due to damages of the fitting protrusion.

As shown in FIGS. 55 and 56 according to still another embodiment of thepresent disclosure, the stator coupling opening 6130 is protruding fromthe body 6110 of the bearing housing 6110 by a predetermined height (H)in an axial direction. Like the aforementioned spacer 2510, the statorcoupling opening 6130 serves to separate the bearing housing from theinner rotor of the stator, thereby circulating heat generated from theinner rotor and radiating the heat. This may enhance a radiating effect.In the present disclosure, the housing coupling opening 2300 may beprotruding from the yoke 2500 of the stator 2000 by a predeterminedheight (H2) in an axial direction. Preferably, the spacing distancebetween the bearing housing 6100 and the inner rotor is sufficientlyobtained by making the stator coupling opening 6130 and the housingcoupling opening 2300 protruding by the predetermined heights (H1, H2).The housing coupling opening 2300 is integrally formed with the waterblocking mounting rib 2700 to have a higher intensity. This may allowthe housing coupling opening 2300 to be easily aligned with the statorcoupling opening 6130. The water blocking mounting rib 2700 serves toprevent water of the washing machine having a dual motor from beingintroduced into the inner rotor, and serves to facilitate the couplingof the bearing housing 6100 to the stator 2000.

According to still another embodiment of the present disclosure, theinner rotor 73 is separately assembled to the outer shaft 81,differently from the aforementioned embodiment where the inner rotor 73and the stator 71 are integrally fabricated by using the bearinghousing. Referring to FIGS. 1, 4 and 5, the inner rotor 73 isfit-assembled to the outer shaft 81 in a separate manner. In this case,the fitting process may be difficult due to the inner rotor 73 having amagnetic component.

In the present disclosure, an assembly auxiliary jig is additionallyextending from the end of the outer shaft 81, thereby guiding an innerrotor assembly. The outer shaft 81 to which the inner rotor 73 isfit-coupled may be implemented as a magnetic substance formed of ametallic material having a high intensity. Accordingly, it is preferablefor the assembly auxiliary jig to be formed of a non-magnetic substancenot influenced by a magnetic component, and to be sufficiently extendingfrom the outer shaft 81.

Hereinafter, will be explained a method for driving a washing machine ina 3D-motion manner by a dual drum, and a control method thereof. Amethod for driving a washing machine, or a washing operation has beenaforementioned in FIG. 58. Referring to FIG. 58, a method for driving awashing machine according to one embodiment of the present disclosurecomprises a washing step of performing a washing process by supplyingwashing water and a detergent (S100), a rinsing step of performing arinsing process by supplying rinsing water (S200), a dehydrating step ofdischarging rinsing water and performing a dehydrating process (S300),and a laundry arranging step of separating laundry from the main drumand the sub drum and releasing an entangled state of the laundry afterthe dehydration process (S400).

In the washing step (S100), a washing process is performed by supplyingwashing water and a detergent. In S100, laundry is washed with moving byrotations of the main drum and the sub drum. The washing step (S100) mayinclude a 3D washing process and a general washing process. In the 3Dwashing process, laundry moves in a circumferential direction byrotations of the main drum and the sub drum. Then, the laundry rotatesat an interface between the main drum and the sub drum by relativemotions of the main drum and the sub drum, and moves in an axialdirection. As indicated by the arrow of FIG. 10, laundry moves in anentangled state belt shape. This is because the laundry moves in acircumferential direction and drops by gravity while rotating.

In the general washing process (S120), laundry moves in acircumferential direction by rotations of the main drum and the subdrum. Differently from the 3D washing process, the main drum and the subdrum integrally rotate without having relative motions performed in thegeneral washing process. In the washing step (S100), the 3D washingprocess and the general washing process may be alternately performed.More concretely, the 3D washing process and the general washing processmay be performed sequentially, or in reverse order. Alternatively, thegeneral washing process may be performed while the 3D washing process isperformed a plurality of times, or vice versa.

In the rinsing step (S200), rinsing water is supplied to remove adetergent, etc. remaining on the laundry. In the dehydrating step(S300), the rinsing water is discharged by a centrifugal force due torotations of the drum, and the laundry is dehydrated. In the laundryarranging step (S400), the laundry is separated from the main drum andthe sub drum, and is out of an entangled-state. The laundry arrangingstep (S400) includes a laundry separating process (S410) of separatingthe laundry from inner surfaces of the main drum and the sub drum, andan entangled state releasing process (S420) of releasing an entangledstate of the laundry while the laundry rotates by relative motions ofthe main drum and the sub drum, and moves in a circumferential directionand an axial direction.

In the laundry separating process (S410), the laundry is separated froman inner circumferential surface of the drum by 3D motions thereof afterthe dehydration process. In the entangled state releasing process(S420), the laundry separated from the inner circumferential surface ofthe drum undergoes 3D motions for a predetermined time so as to be outof an entangled state. The main drum and the sub drum have to integrallyrotate so as to remove water by a centrifugal force during a dehydrationprocess. In this case, the laundry may be in an entangled state.Accordingly, required is the entangled state releasing process. Thelaundry separating process and the entangled state releasing process maybe consecutively performed. Alternatively, the laundry separatingprocess may be performed firstly, and then the entangled state releasingprocess may be performed after a predetermined time has lapsed. Thelaundry separating process and the entangled state releasing processneed not be performed for a long time. It is enough for the laundryseparating process and the entangled state releasing process to beperformed for a time duration for which the laundry is separated fromthe inner circumferential surface of the drum and the laundry is out ofan entangled state. The reason is because dehydrated laundry may havedamages when the two drums perform relative motions for a long time.

If the washing machine is implemented as a washing machine for dualpurposes of washing and drying, the method may further comprise a dryingstep of drying the laundry (S500) after the laundry arranging step(S400). Under this configuration, the laundry is separated from the drumthrough 3D motions after a dehydrating process, and then is out of anentangled state so as to prevent wrinkles. In a washing machine for dualpurposes of washing and drying, the laundry may be arranged before adrying step so as to prevent wrinkles, etc. occurring during the dryingstep. The method for driving a washing machine may further comprise alaundry automatic-drawing step of drawing the laundry to the outside byrelative motions of the main drum and the sub drum (S600) after thedrying step (S500).

The laundry automatic-drawing step (S600) is performed only after a door21 of the washing machine has opened. FIG. 57 illustrates motions of thelaundry by the laundry automatic-drawing step. Referring to FIG. 57,once the door 21 disposed on a front surface of a body 10 has opened,the laundry is discharged to the outside (indicated by the arrow of G)by relative motions of the main drum and the sub drum. The reason isbecause the laundry may be discharged to the outside of the drum whenthe sub drum rapidly rotates, since the laundry moves in an axialdirection by relative motions of the main drum and the sub drum as shownin FIG. 10. Under this configuration, the laundry is automatically drawnout in a simple manner by relative motions of the main drum and the subdrum after the operation of the washing machine has ended. This mayenhance a use's convenience.

The method for driving a washing machine comprises a laundry separatingstep (S410) of separating the laundry from the inner surfaces of themain drum and the sub drum by relative motions of the main drum and thesub drum through the driving motor after the dehydrating step, and anentangled state releasing step (S420) of releasing an entangled state ofthe laundry which is rotating in a circumferential direction and anaxial direction by relative motions of the main drum and the sub drum.And, the method may further comprise a laundry automatic-drawing step(S600) of performing relative motions of the main drum and the sub drumby the driving motor so that the laundry may be discharged to theoutside of the door after the door has opened. The laundry separatingstep, the entangled state releasing step and the laundryautomatic-drawing step have been explained on the basis of theaforementioned driving motor, and thus detailed explanations thereofwill be omitted.

FIG. 59 illustrates a method for controlling the washing machine.Referring to FIG. 59, the driving motor 70 controls the main drum 50 andthe sub drum 60 to perform relative motions by independently rotatingthe outer rotor 72 and the inner rotor 73. This control by the drivingmotor may be performed by a controller 110 of the washing machine. Thecontroller 110 controls the operation of the driving motor bytransmitting a preset signal to the driving motor in each step. Variousrelative motions of the main drum and the sub drum by the driving moorare illustrated in FIG. 60. The driving motor controls the sub drum andthe main drum to rotate in opposite directions. Preferably, the sub drumis controlled to rotate more rapidly than the main drum. This relativemotion is illustrated in FIG. 60A. Referring to FIG. 60A, the main drum50 rotates in a clockwise direction (indicated by the arrow of E), andthe sub drum 60 rotates in a counterclockwise direction (indicated bythe arrow of F). The main drum 50 and the sub drum 60 rotate in oppositedirections in a state that a rotation speed of the sub drum (the size ofthe arrow of F) is faster than a rotation speed of the main drum (thesize of the arrow of E).

The driving motor may allow the sub drum and the main drum to rotate inthe same direction with different rotation speeds. Preferably, the subdrum is controlled to rotate more rapidly than the main drum. Thisrelative motion is illustrated in FIG. 60B. Referring to FIG. 60B, themain drum 50 rotates in a counterclockwise direction (indicated by thearrow of E), and the sub drum 60 rotates in a counterclockwise direction(indicated by the arrow of F). The main drum 50 and the sub drum 60rotate in the same directions in a state that a rotation speed of thesub drum (the size of the arrow of F) is faster than a rotation speed ofthe main drum (the size of the arrow of E). The driving motor may allowonly the sub drum to rotate. This relative motion is illustrated in FIG.60C. Referring to FIG. 60C, the main drum 50 is fixed, and the sub drum60 rotates in a counterclockwise direction (indicated by the arrow ofF). Under these configurations, the main drum and the sub drum mayperform various relative motions under controls of the driving motor.This may allow the laundry inside the drum to perform 3D motions. Underthese configurations, the laundry performs 3D motions by relativemotions of the drums controlled by the driving motor. This may preventwrinkles of the laundry, and allow the laundry to be automatically drawnout.

According to still another embodiment of the present disclosure, awashing step in a method for driving a washing machine is performed in amore divided manner. The method for driving a washing machine has beenaforementioned in FIG. 8. Referring to FIG. 61, a method for driving awashing machine according to one embodiment of the present disclosurecomprises a washing step of performing a washing process by supplyingwashing water and a detergent (S100), a rinsing step of performing arinsing process by supplying rinsing water (S200), and a dehydratingstep of discharging rinsing water and performing a dehydrating process(S300). The washing step (S100) includes a 3D washing process (S110) ofrotating laundry and moving the laundry in a circumferential directionand an axial direction by relative motions of the main drum and the subdrum. As aforementioned, the washing step (S100) includes a 3D washingprocess (S110) and a general washing process (S120). In the washing stepfor performing a washing process by supplying washing water and adetergent, the driving motor controls the main drum and the sub drum toperform relative motions so that the laundry may rotate and may move ina circumferential direction and an axial direction.

FIG. 62 illustrates a method for controlling a washing machine accordingto another embodiment of the present disclosure. In this embodiment ofFIG. 62, a washing process is differently performed according to alaundry amount. More concretely, the driving motor controls the maindrum and the sub drum according to a laundry amount measured in thewashing step for performing a washing process by supplying washing waterand a detergent. For instance, the driving motor controls the main drumand the sub drum to perform relative rotations so that laundry may movein an axial direction and a circumferential direction with rotations, orcontrols the main drum and the sub drum to integrally rotate so thatlaundry may move only in a circumferential direction. This embodiment ofFIG. 62 is applied to the washing machine for 3D motions. In thisembodiment, a laundry amount (M) has to be measured in advance (S150).The measurement may be performed based on a load of a drum by rotatingthe drum at an initial stage. Alternatively, the measurement may beperformed by an additional load sensor.

Washing processes are performed differently according to a measuredlaundry amount (S160) based on a maximum load (Mmax) of the drivingmotor 70. More concretely, when a laundry amount is less than ⅓ of themaximum load of the driving motor, the driving motor rotates the maindrum and the sub drum in opposite directions (S171). When a laundryamount is more than ⅓ and less than ⅔ of the maximum load of the drivingmotor, the driving motor rotates the main drum and the sub drum in thesame direction with different speeds (S172). When a laundry amount ismore than ⅔ of the maximum load of the driving motor, the driving motorintegrally rotates the main drum and the sub drum in the same direction(S173). Under these configurations, the laundry performs general planarmotions or 3D motions according to the amount. This may implement anoptimum washing performance without causing an overload to the drivingmotor.

Hereinafter, the method for driving a washing machine by varying RPMs ofthe main drum and the sub drum will be explained in more details.Referring to FIG. 63, a control unit 100 may control currents to beapplied to inner and outer winding portions of the driving motor 70.This may allow the inner and outer rotors to rotate independently. As aresult, as shown in FIG. 5, the main drum 50 and the sub drum 60 mayrotate independently by one driving motor 70. Referring to FIGS. 1 and63, the control unit 100 may be installed in a control panel 30, or in acontainer additionally provided at one side in the washing machine. Thecontrol unit 100 is generally implemented as one or more PCBs. Thewashing machine further comprises a storage unit 400 configured to storetherein a driving program, information on processes of washing, drying,dehydration, etc., and so on. The washing machine further comprises aninput unit 500 having each type of manipulation buttons disposed on thecontrol panel 30. And, the washing machine may further comprise anoutput unit 600 configured to output a time, a temperature, a state, anerror, etc. The control unit 100 initially operates the outer rotor 72and the inner rotor 73 with the same starting RPM smaller than targetRPMs of the outer rotor 72 and the inner rotor 73. The target RPM may bevariable according to a laundry amount and a motion type, and each ofthe outer rotor and the inner rotor may have a set target RPM. Thestarting RPM may be a target RPM of the inner rotor.

Referring to FIG. 64, the driving motor of the washing machine starts tooperate with a target RPM of the inner rotor. After a predetermined timehas lapsed, the outer rotor 72 rotates with increasing a speed into apreset target RPM. On the other hand, the inner rotor 73 rotates withmaintaining the starting RPM. Here, the starting RPM may be set as avalue rather than the target RPM of the inner rotor. If the inner rotorand the outer rotor start to operate and at the same time rotate withdifferent target RPMs, an over current may be applied to the drivingmotor. As shown in FIG. 64, an over current is applied to the outerrotor set to have a high RPM, and a large amount of heat is generatedfrom the motor. On the other hand, if the driving motor starts tooperate in a state that the inner rotor and the outer rotor have thesame RPM, a load of the motor is reduced and the amount of heat isreduced. This may prevent a failure of the initial operation of thedriving motor due to an over current.

Referring to FIG. 63 back, the washing machine according to anotherembodiment includes the control unit 100 configured to operate the outerrotor 72 and the inner rotor 73 of the driving motor 70, respectively.The control unit 100 is connected to the input unit 500, the output unit600, a laundry amount detection unit 200 and a temperature detectionunit 300. The control unit 100 controls one of the outer rotor 72 andthe inner rotor 73 having a larger torque to firstly start to operate.The same configuration of the washing machine as that aforementioned inone embodiment will not be explained.

FIG. 65 is a graph showing temperature changes of the inner rotor andthe outer rotor after an initial operation (including restart).Referring to FIG. 65, the inner rotor 73 has a greater temperature thanthe outer rotor 72 according to time lapses. The reason is because alarge amount of current is applied to the inner rotor 73 since the innerrotor 73 starts to operate faster than the outer rotor 72. If the outerrotor and the inner rotor start to operate and at the same time rotatewith target RPMs differently set for various movements, an over currentis applied to the driving motor. Especially, an over current is appliedto one rotor having a relatively small torque, and the amount of heatgenerated from the motor is increased. The control unit 100 comparestorques of the outer rotor 72 and the inner rotor 73 with each other,and controls one rotor having a relatively large torque to firstly startto operate. For instance, when the inner rotor 73 has a larger torque,the control unit 100 controls the inner rotor to firstly start tooperate. This may reduce a load of the outer rotor having a smallertorque, and may prevent an excessive amount of heat. The outer rotor andthe inner rotor have different torques for 3D motions.

Referring to FIG. 63, the washing machine further comprises a laundryamount detection unit 200 configured to detect a laundry amount. If apredetermined time lapses after the driving motor 70 has started tooperate, the control unit 100 controls a rotation direction or an RPM ofeach of the outer rotor and the inner rotor according to a laundryamount. For instance, when a laundry amount is less than a referencelaundry amount, the control unit 100 rotates the main drum and the subdrum by driving the outer rotor and the inner rotor in oppositedirections since the driving motor has a sufficient torque. This mayallow the laundry to perform 3D motions, and may shorten a washing time.Here, the reference laundry amount may be set as 4 Kg, 6 Kg, etc.

On the other hand, when a laundry amount is more than the referencelaundry amount, the control unit 100 rotates the outer rotor and theinner rotor in the same direction with different RPMs. That is, thecontrol unit 100 controls the main drum and the sub drum to performrelative motions with different RPMs. This may allow the laundry toperform enhanced movements. Furthermore, when a laundry amount is morethan the reference amount, the control unit 100 may reduce the amount ofheat generated from the driving motor by more reducing the RPMs of theouter rotor and the inner rotor as the laundry amount increases.

As another example, when a laundry amount is less than a first referencelaundry amount, the control unit 100 rotates the outer rotor and theinner rotor in opposite directions. When a laundry amount is more than asecond reference laundry amount greater than the first reference laundryamount, the control unit 100 rotates the outer rotor and the inner rotorin the same direction. The first reference laundry amount and the secondreference laundry amount may be preset based on experiments, etc., andmay be set as 4 Kg, 6 Kg, 8 Kg, etc.

The control unit 100 allows the laundry to perform 3D motions bydifferently setting rotation directions and RPMs according to a laundryamount. And, the control unit 100 enhances the stability of the washingmachine by operating the driving motor with consideration of a heatgeneration amount or torque of the driving motor. For instance, when alaundry amount is more than the first reference laundry amount and lessthan the second reference laundry amount, the control unit 100 controlsrotation directions or RPMs of the outer rotor and the inner rotoraccording to a heat generation amount or torque of the driving motor.When a laundry amount is more than the first reference laundry amountand less than the second reference laundry amount, the control unit 100controls the outer rotor and the inner rotor to continuously rotate inopposite directions, and reduces relative speeds of the outer rotor andthe inner rotor as the laundry amount increases. This may reduce theamount of heat generated from the driving motor. When a laundry amountis more than the second reference laundry amount, the control unit 100reduces the relative speeds of the outer rotor and the inner rotor asthe laundry amount increases.

The washing machine may further comprise a temperature detection unit300 provided at the outer rotor or the inner rotor, and configured todetect a temperature. The washing machine is provided with a temperaturedetection unit such as a thermistor, and the control unit 100 compares adetected temperature of the driving motor with a preset referencetemperature. When a detected temperature is more than a referencetemperature, the control unit 100 changes a rotation direction or an RPMof the outer rotor or the inner rotor. For instance, the control unit100 may lower a temperature of the driving motor by reducing orcompensating for vibrations by making RPMs of the outer rotor and theinner rotor the same.

Referring to FIG. 66, a method for controlling a washing machineaccording to one embodiment of the present disclosure comprisesinitially operating the driving motor with the same starting RPM smallerthan target RPMs of the outer rotor and the inner rotor (S130), andoperating the outer rotor and the inner rotor with the respective targetRPMs when a predetermined time lapses after initially-operating thedriving motor (S150). The washing machine initially operates the outerrotor and the inner rotor with the same starting RPM smaller than targetRPMs of the outer rotor and the inner rotor (S130). The target RPM maybe variable according to a laundry amount, a motion type, etc., and eachof the outer rotor and the inner rotor may have a set target RPM (S120).For instance, if a user puts laundry into the washing machine and theninputs an operation command (S10), the washing machine detects a laundryamount (S110) and calculates a target RPM according to the detectedlaundry amount (S120). Here, the starting RPM may be a target RPM of theinner rotor.

Referring to FIG. 64, the driving motor of the washing machine starts tooperate with a target RPM of the inner rotor (S130). After apredetermined time has lapsed (S140), the outer rotor 72 rotates withincreasing a speed into a preset target RPM (S150). On the other hand,the inner rotor rotates with maintaining the starting RPM. Here, thestarting RPM may be set as a value rather than the target RPM of theinner rotor. If the inner rotor and the outer rotor start to operate andat the same time rotate with different target RPMs, an over current maybe applied to the driving motor. As shown in FIG. 64, an over current isapplied to the outer rotor set to have a high RPM, and a large amount ofheat is generated from the motor. On the other hand, if the drivingmotor starts to operate in a state that the inner rotor and the outerrotor have the same RPM, a load of the motor is reduced and the amountof heat is reduced. This may prevent a failure of the initial operationof the driving motor due to an over current.

Referring to FIG. 67, a method for controlling a washing machineaccording to another embodiment of the present disclosure comprisescomparing torques of the outer rotor and the inner rotor (S220), firstlyinitial-operating one rotor having a larger torque and theninitial-operating another rotor having a smaller torque based on acomparison result (S230), and operating the outer rotor and the innerrotor with respective target RPMs if a predetermined time lapses afterthe driving motor 70 has started to operate (S240).

FIG. 65 is a graph showing temperature changes of the inner rotor andthe outer rotor after an initial operation (including restart).Referring to FIG. 65, the inner rotor has a greater temperature and agreater change rate than the outer rotor according to time lapses. Thereason is because a large amount of current is applied to the innerrotor since the inner rotor starts to operate faster than the outerrotor. If the outer rotor and the inner rotor start to operate and atthe same time rotate with target RPMs differently set for variousmovements, an over current is applied to the driving motor. Especially,an over current is applied to one rotor having a relatively smalltorque, and the amount of heat generated from the motor is increased.The washing machine compares torques of the outer rotor and the innerrotor with each other (S220), and controls one rotor having a relativelylarge torque to firstly start to operate (S230). For instance, when theinner rotor has a larger torque, the washing machine firstly initiallyoperates the inner rotor, and then initially operates the outer rotor(S233, S234). This may reduce a load of the outer rotor having a smallertorque, and may prevent an excessive amount of heat. On the other hand,when the outer rotor has a larger torque, the washing machine firstlyinitially operates the outer rotor, and then initially operates theinner rotor (S231, S232). The outer rotor and the inner rotor havedifferent torques for 3D motions. Then, the washing machine operates thedriving motor by differently setting target RPMs and rotation directionsaccording to a detected laundry amount (S240).

The washing machine controls rotation directions or RPMs of the outerrotor and the inner rotor according to a laundry amount if apredetermined time lapses after the driving motor 70 has started tooperate. For instance, when a laundry amount is less than a referencelaundry amount, the washing machine rotates the main drum and the subdrum by driving the outer rotor and the inner rotor in oppositedirections since the driving motor has a sufficient torque. This mayallow the laundry to perform 3D motions, and may shorten a washing time.Here, the reference laundry amount may be set as 4 Kg, 6 Kg, etc. On theother hand, when a laundry amount is more than the reference laundryamount, the washing machine rotates the outer rotor and the inner rotorin the same direction with different RPMs. That is, the washing machinecontrols the main drum and the sub drum to perform relative motions withdifferent RPMs. This may allow the laundry to perform enhancedmovements. Furthermore, when a laundry amount is more than the referenceamount, the washing machine may reduce the amount of heat generated fromthe driving motor by more reducing the RPMs of the outer rotor and theinner rotor as the laundry amount increases.

Referring to FIG. 68, as another example, when a laundry amount is lessthan a first reference laundry amount (S310), the washing machinerotates the outer rotor and the inner rotor in opposite directions(S320). When a laundry amount is more than a second reference laundryamount greater than the first reference laundry amount (S330), thewashing machine rotates the outer rotor and the inner rotor in the samedirection (S340). The first reference laundry amount and the secondreference laundry amount may be preset based on experiments, etc., andmay be set as 4 Kg, 6 Kg, 8 Kg, etc.

The washing machine allows the laundry to perform 3D motions bydifferently setting rotation directions and RPMs according to a laundryamount. And, the washing machine has an enhanced stability by operatingthe driving motor with consideration of a heat generation amount ortorque of the driving motor. For instance, when a laundry amount is morethan the first reference laundry amount and less than the secondreference laundry amount, the washing machine controls rotationdirections or RPMs of the outer rotor and the inner rotor according to aheat generation amount or torque of the driving motor (S350). When alaundry amount is more than the first reference laundry amount and lessthan the second reference laundry amount, the washing machine controlsthe outer rotor and the inner rotor to continuously rotate in oppositedirections (S372), and reduces relative speeds of the outer rotor andthe inner rotor as the laundry amount increases (S373). This may reducethe amount of heat generated from the driving motor. When a laundryamount is more than the second reference laundry amount (S361), thewashing machine reduces the relative speeds of the outer rotor and theinner rotor as the laundry amount increases (S362).

The washing machine may be further configured to detect a temperature ofthe inner rotor. Referring to FIG. 69, the washing machine is providedwith a temperature detection unit such as a thermistor at the drivingmotor to detect a temperature of the driving motor (S410), and comparesthe detected temperature with a preset reference temperature (S421,S431). When the detected temperature is more than a referencetemperature, the washing machine changes a rotation direction or an RPMof the outer rotor or the inner rotor (S422, S432). For instance, thewashing machine may lower a temperature of the driving motor by reducingor compensating for vibrations by making RPMs of the outer rotor and theinner rotor the same. On the other hand, if the detected temperature islower than the reference temperature, the washing machine maintains thecurrent state (S440).

According to still another embodiment of the present invention, as shownin FIG. 63, the control unit 100 drives the inner rotor 73 and the outerrotor 72 into particular RPMs, respectively, and applies a brakingcommand to the inner rotor 73 and the outer rotor 72. Then, the controlunit 100 detects a first laundry amount inside the main drum 50 and asecond laundry amount inside the sub drum 60 based on braking times ofthe inner and outer rotors. The particular RPMs of the inner rotor andthe outer rotor may be set as different values, or may be set as thesame value (e.g., 150 RPM, 160 RPM, etc.) In the aforementioneddescription, the first laundry amount and the second laundry amount aredetected based on the braking times. However, the first laundry amountand the second laundry amount may be detected based on the number ofpulses by rotation.

The control unit 100 may brake the outer rotor and the inner rotor indifferent manners or in the same manner. That is, the control unit 100may brake both of the inner and outer rotors using generated power, ormay brake both of the inner and outer rotors using redundant power.Alternatively, the control unit 100 may brake one of the inner and outerrotors using generated power, and brake another of the two usingredundant power. Explanations about configurations of the generatedpower braking and the redundant power braking, e.g., resistance, circuitconnection, etc. will be omitted.

The washing machine further comprises a current detector 200 configuredto detect a first current and a second current applied to the innerrotor and the outer rotor, respectively. The washing machine furthercomprises an output unit 300 configured to display one of the firstlaundry amount, the second laundry amount, and a final laundry amountdetermined based on the first and second laundry amounts. The washingmachine further comprises a storage unit 400 configured to store thereina driving program for the washing machine, information on washing,drying, dehydrating, etc. The washing machine further comprises an inputunit 500 including all types of manipulation buttons disposed on acontrol panel 30. The output unit 300 may display time, temperature,state, error, etc.

FIG. 70 is a graph showing RPM change of each rotor when both of theouter rotor 72 and the inner rotor 73 undergo generated power brakingFIG. 71 is a graph showing currents applied to the inner and outerrotors of FIG. 70. Referring to FIG. 70, the control unit 100 initiallydrives the inner and outer rotors, thereby increasing RPMs of the innerand outer rotors to a particular value, 160 RPM. Then, the control unit100 generates a braking command for the inner and outer rotors, andoutputs the generated braking command to the inner and outer rotors.Preferably, the braking command is simultaneously output to the innerrotor 73 and the outer rotor 72 for a minimized change of the laundryamount. In the case of braking both of the inner and outer rotors usinggenerated power, the outer rotor (RPM2) is firstly braked than the innerrotor (RPM1) as shown in FIG. 70. Referring to FIG. 71, current (I1)applied to the inner rotor 73 is larger than current (I2) applied to theouter rotor 72, and braking time (T1) of the inner rotor 73 is longerthan braking time (T2) of the outer rotor 72.

FIG. 72 is a graph showing an RPM change of each rotor when the outerrotor 72 undergoes redundant power braking and the inner rotor 73undergoes generated power braking FIG. 73 is a graph showing currentsapplied to the inner and outer rotors of FIG. 72. Referring to FIG. 72,the control unit 100 initially drives the inner and outer rotors,thereby increasing RPMs of the inner and outer rotors to a particularvalue, 160 RPM. Then, the control unit 100 generates a braking commandfor the inner and outer rotors, and outputs the generated brakingcommand to the inner and outer rotors. Preferably, the braking commandis simultaneously output to the inner rotor 73 and the outer rotor 72for a minimized change of the laundry amount. In the case of braking theinner rotor 73 using generated power and braking the outer rotor 72using redundant power, the inner rotor (RM1) is firstly braked than theouter rotor (RPM2′) as shown in FIG. 72. Unlike in FIG. 70, the outerrotor undergoing redundant power braking has a larger RPM than the outerrotor undergoing generated power braking (RPM2′>RPM2). Referring to FIG.73, current (I1) applied to the inner rotor undergoing generated powerbraking is larger than current (I2) applied to the outer rotor 72undergoing redundant power braking. That is, the inner rotor undergoinggenerated power braking is instantaneously applied with a large current,and has a braking time (T1) shorter than that of the inner rotorundergoing redundant power braking. On the other hand, the outer rotorundergoing redundant power braking has an immediate current change to‘0’ upon receipt of a braking command, and has a braking time (T2)longer than that of the outer rotor undergoing generated power brakingas shown in FIGS. 72 and 73.

Referring to FIGS. 1 and 74, a washing machine according to stillanother embodiment of the present invention comprises a main body 10which forms an outer appearance; a tub 40 disposed within the main body10; a main drum 50 rotatably mounted in the tub 40, and accommodatinglaundry therein; a sub drum 60 mounted in the main drum 50 so as to berelatively rotatable with respect to the main drum 50; a driving motor70 including a stator 71, an outer rotor 72 connected to the sub drum 60and rotating outside the stator 71, and an inner rotor 73 connected tothe main drum 50 and rotating inside the stator 71; and a control unit100 configured to drive the outer rotor 72 and the inner rotor 73.

The control unit 100 includes a master controller 110 configured todrive the inner rotor 73, and to detect the first laundry amount basedon the braking time of the inner rotor; and a slave controller 120connected to the master controller 110, configured to drive the outerrotor 72, and to detect the second laundry amount based on the brakingtime of the outer rotor. The master controller 110 generates a brakingcommand for the outer rotor 72, and transmits the braking command to theslave controller 120. Then, the master controller 110 generates abraking command for the inner rotor 73 after a particular time haslapsed. Here, the particular time is determined based on a communicationspeed between the master controller and the slave controller, i.e.,communication delay. For instance, the particular time may be set as 50ms, etc. The master controller and the slave controller are configuredas different microcomputers. The master controller and the slavecontroller output the braking commands to the inner rotor and the outerrotor, simultaneously.

After outputting the braking commands, the master controller 110 detectsa first laundry amount inside the main drum 50 driven by the inner rotor73. And, the slave controller 120 detects a second laundry amount insidethe sub drum 60 driven by the outer rotor 72. Here, the mastercontroller and the slave controller

detect the first and second laundry amounts based on the braking time ofthe outer rotor, and based on the number of pulses until the outer rotorstops rotating. The particular RPMs of the inner rotor and the outerrotor may be set as different values, or may be set as the same value(e.g., 150 RPM, 160 RPM, etc.) In the aforementioned description, thefirst laundry amount and the second laundry amount are detected based onthe braking times. However, the first laundry amount and the secondlaundry amount may be detected based on the number of pulses byrotation.

The control unit 100 may brake the outer rotor and the inner rotor indifferent manners or in the same manner. That is, the control unit 100may brake both of the inner and outer rotors using generated power, ormay brake both of the inner and outer rotors using redundant power.Alternatively, the control unit 100 may brake one of the inner and outerrotors using generated power, and brake another of the two usingredundant power. Referring to FIGS. 70 to 73, the master controller andthe slave controller initially drive the inner rotor and the outerrotor, thereby increasing RPMs of the inner and outer rotors to aparticular value, 160 RPM. Then, the master controller generates abraking command for the outer rotor, and transmits the generated brakingcommand to the slave controller. And, the master controller generates abraking command for the inner rotor. The master controller and the slavecontroller output the braking commands to the inner rotor and the outerrotor, simultaneously, with consideration of a communication delaytherebetween. The master controller detects a first laundry amount basedon a braking time of the rotor (i.e., time taken for the inner rotor tostop upon receipt of the braking command). And, the slave controllerdetects a second laundry amount based on a braking time of the outerrotor (i.e., time taken for the outer rotor to stop upon receipt of thebraking command), and transmits information on the second laundry amountto the master controller. Then, the master controller determines a finallaundry amount based on the first and second laundry amounts in thefollowing manners. For instance, the first and second laundry amountsmay be added to each other in a preset ratio. Alternatively, the firstlaundry amount or the second laundry amount may be set as the finallaundry amount. Most simply, the first laundry amount may be set as thefinal laundry amount. FIGS. 70 and 71 show a case where a laundry amountis detected after braking the inner and outer rotors using generatedpower. FIGS. 72 and 73 show a case where a laundry amount is detectedafter braking the inner rotor using generated power and braking theouter rotor using redundant power.

Referring to FIG. 75, there is provided a laundry amount detectingmethod for a washing machine according to an embodiment of the presentinvention, the washing machine comprising a main body which forms anouter appearance; a tub disposed within the main body; a main drumrotatably mounted in the tub, and accommodating laundry therein; a subdrum mounted in the main drum so as to be relatively rotatable withrespect to the main drum; and a driving motor including a stator, anouter rotor connected to the sub drum and rotating outside the stator,and an inner rotor connected to the main drum and rotating inside thestator, the method comprising: initially driving the inner rotor and theouter rotor (S110); braking the inner rotor and the outer rotor (S130)when RPMs of the inner rotor and the outer rotor reach a particularvalue (S120); and detecting a first laundry amount inside the main drumand a second laundry amount inside the sub drum based on braking timesof the inner rotor and the outer rotor (S140, S150). The method furthercomprises displaying one of the first laundry amount, the second laundryamount, and a final laundry amount determined based on the first andsecond laundry amounts (S160).

Referring to FIG. 70, the washing machine initially drives the innerrotor and the outer rotor, and increases RPMs of the inner and outerrotors to a particular value, 160 RPM (S110, S120). Then, the washingmachine generates braking commands for the inner and outer rotors, andoutputs the braking commands to the inner and outer rotors (S130). Here,the washing machine simultaneously outputs the braking command to theinner and outer rotors for minimization of change of the laundry amountdue to braking. In case of braking both of the inner and outer rotorsusing generated power, the outer rotor (RPM2) is firstly braked than theinner rotor (RPM1) as shown in FIG. 70. Referring to FIG. 71, current(I1) applied to the inner rotor 73 is larger than current (I2) appliedto the outer rotor 72, and braking time (T1) of the inner rotor 73 islonger than braking time (T2) of the outer rotor 72.

In case of braking the inner rotor 73 using generated power and brakingthe outer rotor 72 using redundant power, the inner rotor (RM1) isfirstly braked than the outer rotor (RPM2′) as shown in FIG. 72. Unlikein FIG. 70, the outer rotor undergoing redundant power braking has alarger RPM than the outer rotor undergoing generated power braking(RPM2′>RPM2). Referring to FIG. 73, current (I1) applied to the innerrotor undergoing generated power braking is larger than current (I2)applied to the outer rotor 72 undergoing redundant power braking. Thatis, the inner rotor undergoing generated power braking isinstantaneously applied with a large current, and has a braking time(T1) shorter than that of the inner rotor undergoing redundant powerbraking. On the other hand, the outer rotor undergoing redundant powerbraking has an immediate current change to ‘0’ upon receipt of a brakingcommand, and has a braking time (T2) longer than that of the outer rotorundergoing generated power braking as shown in FIGS. 72 and 73.

The washing machine detects a first laundry amount and a second laundryamount based on the braking times (T1, T2) (S150). The washing machinemay display one of the first laundry amount, the second laundry amount,and the final laundry amount determined based on the first and secondlaundry amounts, on a screen, through an output unit (S160). The washingmachine determines the final laundry amount based on the first andsecond laundry amounts in the following manners. For instance, the firstand second laundry amounts may be added to each other in a preset ratio.Alternatively, the first laundry amount or the second laundry amount maybe set as the final laundry amount. Most simply, the first laundryamount may be set as the final laundry amount.

Referring to FIG. 76, there is provided a laundry amount detectingmethod for a washing machine according to another embodiment of thepresent invention, the washing machine comprising a main body whichforms an outer appearance; a tub disposed within the main body; a maindrum rotatably mounted in the tub, and accommodating laundry therein; asub drum mounted in the main drum so as to be relatively rotatable withrespect to the main drum; a driving motor including a stator, an outerrotor connected to the sub drum and rotating outside the stator, and aninner rotor connected to the main drum and rotating inside the stator; amaster controller configured to drive the inner rotor; and a slavecontroller configured to drive the outer rotor, the method comprising:initially driving the inner rotor and the outer rotor by the mastercontroller and the slave controller, respectively; braking the innerrotor and the outer rotor by the master controller, when RPMs of theinner rotor and the outer rotor reach a particular value; and detectinga first laundry amount inside the main drum and a second laundry amountinside the sub drum by the master controller and the slave controller,based on braking times of the inner rotor and the outer rotor.

Referring to FIGS. 70 to 73, the master controller and the slavecontroller initially drive the inner rotor and the outer rotor, therebyincreasing RPMs of the inner and outer rotors into a particular RPM, 160RPM (S210, S220). Then, the master controller generates a brakingcommand for the outer rotor, and transmits the generated braking commandto the slave controller (S231, S232). And, the master controllergenerates a braking command for the inner rotor (S233). The mastercontroller and the slave controller output the braking commands to theinner rotor and the outer rotor, simultaneously, with consideration of acommunication delay therebetween. The master controller detects a firstlaundry amount based on a braking time of the inner rotor (i.e., timetaken for the inner rotor to stop upon receipt of the braking command)(S250). And, the slave controller detects a second laundry amount basedon a braking time of the outer rotor (i.e., time taken for the outerrotor to stop upon receipt of the braking command), and transmitsinformation on the second laundry amount to the master controller(S250). Then, the master controller determines a final laundry amountbased on the first and second laundry amounts in the following manners.For instance, the first and second laundry amounts may be added to eachother in a preset ratio. Alternatively, the first laundry amount or thesecond laundry amount may be set as the final laundry amount. Mostsimply, the first laundry amount may be set as the final laundry amount.The washing machine may display, on a screen, one of the first laundryamount, the second laundry amount, and the final laundry amountdetermined based on the first and second laundry amounts (S260).

As aforementioned, in the washing machine and the laundry amountdetecting method thereof according to the present invention, two drumsare independently driven to allow laundry to perform 3D motions invarious manners. Owing to the 3D motions of the laundry, washingperformance of the washing machine can be enhanced, and washing time canbe reduced. In the present invention, the washing machine has enhancedwashing performance, through 3D motions of laundry, with considerationof torque distribution due to driving of two drums, a mechanical forceapplied to the laundry, and movements of the laundry. The washingmachine is provided with two drums, and a single driving motor forindependently driving the two drums. Since a laundry amount is detectedwith respect to each drum, the laundry amount can be precisely detected.In the present invention, the laundry amounts inside the two drums aredetected in different manners. This can allow the laundry amount to bemore precisely detected, and can reduce the amount of washing water andelectricity required to perform washing, rinsing and dehydrationprocesses.

What is claimed is:
 1. A washing machine including: a main body definingan outer appearance; a tub disposed within the main body; a main drumrotatably mounted in the tub; a sub drum mounted in the main drum to berelatively rotatable with respect to the main drum; an outer shaft forrotating the main drum; an inner shaft for rotating the sub drum, beingdisposed inside the outer shaft; and a driving motor having a stator, anouter rotor connected to the inner shaft that is rotatable outside thestator, and an inner rotor connected to the outer shaft that isrotatable inside the stator, wherein the driving motor independentlydrives the main drum and the sub drum.
 2. The washing machine of claim1, wherein the driving motor drives the inner rotor and the outer rotorindependently, and wherein the main drum and the sub drum are drivenindependent of each other.
 3. The washing machine of claim 2, wherein anindependent drive between the outer rotor and the inner rotor inducesrotations of laundry by a difference in rotation speed between thedrums.
 4. The washing machine of claim 1, wherein the main drum and thesub drum move the laundry in a direction by virtue of relative rotationstherebetween, allowing the laundry to perform three-dimensional motionswhile rotating within the main drum and the sub drum.
 5. The washingmachine of claim 4, wherein an inner circumferential surface of the maindrum is divided into a first surface that does not face the outercircumferential surface of the sub drum and a second surface that facesthe outer circumferential surface of the sub drum, and wherein thelaundry is moved in the axial direction by relative motions between thefirst surface of the inner circumferential surface of the main drum andthe inner circumferential surface of the sub drum.
 6. The washingmachine of claim 5, further comprising a plurality of main drum liftersprotruding from the inner circumferential surface of the main drumtoward the inside in a radial direction, and a plurality of sub drumlifters protruding from an inner circumferential surface of a sub drumtoward the inside in a radial direction, wherein the plurality of maindrum lifters are provided on the first surface, and wherein a lengthratio of the main drum lifter and the sub drum lifter in an axialdirection is proportional to a length of the first surface of the innercircumferential surface of the main drum and a length of the innercircumferential surface of the sub drum.
 7. The washing machine of claim6, wherein the main drum lifters and the sub drum lifters have apredetermined angle from an axial direction.
 8. The washing machine ofclaim 6, wherein the main drum lifters or the sub drum lifters areformed to have a straight inclination or a curve inclination along anaxial direction.
 9. The washing machine of claim 1, further comprising amain drum spider to connect the main drum to the outer shaft, and a subdrum spider to connect the sub drum to the inner shaft, wherein separatespiders are employed for the respective drums, and wherein the main drumand the sub drum are independently driven by the driving motor.
 10. Thewashing machine of claim 9, wherein the sub drum spider comprises ashaft coupling portion coupled to the inner shaft, and a plurality ofdrum fixing portions radially extending from the shaft coupling portion,and ends of the drum fixing portions are fixable onto the sub drum back.11. The washing machine of claim 9, wherein the main drum spidercomprises a shaft coupling portion coupled to the outer shaft, a spidersupporting portion radially extending from the shaft coupling portion,and a drum fixing portion disposed at an end of the spider supportingportion, and the drum fixing portion is fixed onto the main drum. 12.The washing machine of claim 9, wherein the sub drum spider is rotatableindependent of the main drum spider.
 13. The washing machine of claim 1,wherein the main drum has openings at front and rear sides, and the subdrum has a sub drum back to form its rear surface, and the sub drum hasa front side open and the rear side closed by the sub drum back.
 14. Thewashing machine of claim 13, wherein the main drum comprises a main drumback to form its rear surfaces, and the main drum and the sub drum havethe front side open and the rear side closed by the main drum back andthe sub drum back, respectively.
 15. The washing machine of claim 13,wherein an outer circumferential surface of the sub drum faces an innercircumferential surface of the main drum, and only a part of the innercircumferential surface of the main drum faces the outer circumferentialsurface of the sub drum.
 16. The washing machine of claim 15, whereinthe sub drum is shorter than the main drum in length in an axialdirection, such that laundry can contact an interface between the subdrum and the main drum.
 17. The washing machine of claim 15, wherein aratio (D2/D1) of a length D2 of an inner circumferential surface of thesub drum in an axial direction with respect to a length D1 of the innercircumferential surface of the main drum in an axial direction is 0˜0.5,and the length D2 of the inner circumferential surface of the sub drumin the axial direction with respect to the length D1 of the innercircumferential surface of the main drum in the axial direction issubstantially ⅓.
 18. The washing machine of claim 15, wherein thewashing machine further comprises a drum guide provided along the innercircumferential surface of the main drum to shield an interval from theouter circumferential surface of the sub drum.
 19. The washing machineof claim 18, wherein the drum guide comprises a body portion protrudinginto the main drum and coupled to the inner surface of the main drum,and a guide portion extending from the body portion toward the innercircumferential surface of the sub drum.
 20. The washing machine ofclaim 15, wherein a reinforcing bead to prevent torsion of the sub drumis provided at an inner circumferential surface or the outercircumferential surface of the sub drum.
 21. The washing machine ofclaim 13, wherein the sub drum comprises a bead protruding into the subdrum along a circumferential surface while being spaced apart from anend portion of the sub drum by a predetermined interval, and a guideportion of a drum guide extends up to the bead of the sub drum.
 22. Thewashing machine of claim 21, wherein the end portion of the sub drum iscurled outwardly along the circumferential surface.
 23. The washingmachine of claim 13, wherein the main drum is divided into a firstportion and a second portion having different inner diameters from eachother, and the inner diameter of the first portion is the same as theinner diameter of the sub drum, and the inner diameter of the secondportion is greater than an outer diameter of the sub drum, therebyshielding the interface between the main drum and the sub drum.
 24. Thewashing machine of claim 1, wherein a rotation shaft of the washingmachine is inclined with respect to a horizontal direction by apredetermined angle.
 25. The washing machine of claim 1, wherein aplurality of lifters are provided on at least one inner circumferentialsurface of the main drum and the sub drum to guide motions of thelaundry.
 26. The washing machine of claim 1, wherein the sub drum has acylindrical portion and a drum back which are integrally formed witheach other as one member.
 27. The washing machine of claim 26, whereinthe receiving portion includes coupling openings for coupling of the subdrum spider, and the sub drum spider includes coupling openingscorresponding to the coupling openings of the receiving portion.
 28. Thewashing machine of claim 1, wherein the sub drum comprises a cylindricalportion and a drum back as independent members, and wherein the drumback is coupled to an outer circumference of the rear of the cylindricalportion to close the rear side.
 29. The washing machine of claim 28,wherein the drum back comprises a receiving portion extendable up to theouter circumference of the drum back, and coupling openings are formedat a rear end portion of the cylindrical portion, and an outercircumference of the drum back is bent in a lengthwise direction of thedrum, and coupling openings are formed at the bent portion.
 30. Thewashing machine of claim 1, wherein the sub drum is assembled bycoupling a cylindrical portion forming an outer circumferential portionof the sub drum to a drum back disposed on a rear surface of the subdrum and coupled with a sub drum spider, receiving the sub drum spiderin a spider receiving portion recessed toward the front of the drumback, and coupling arm end portions of the sub drum spider using boltsthrough coupling openings formed at the rear end portion of thecylindrical portion of the sub drum and a bent outer circumference ofthe drum back.
 31. A drum assembling method for a washing machineincluding a main drum and a sub drum disposed within a tub fixed to amain body and driven independent of each other, and a driving motorhaving a stator, an outer rotor and an inner rotor to independentlydrive the main drum and the sub drum, the method comprising: coupling ashaft for transferring a driving force from the driving motor to themain and sub drums to a spider to fabricate a shaft-spider assembly,coupling the shaft-spider assembly to the rear of the sub drum, couplingthe sub drum to the main drum, and coupling the shaft-spider assembly tothe rear of the main drum.
 32. The method of claim 31, wherein in thefabricating of the shaft-spider assembly, after a main drum spider iscoupled to an outer shaft to transfer a driving force from the innerrotor to the main drum, and a sub drum spider is coupled to an innershaft to transfer a driving force from the outer rotor to the sub drum,the inner shaft is coupled into the outer shaft.
 33. The method of claim31, wherein the inner shaft is coupled into the outer shaft, and then abearing is press-fitted, and after the bearing is press-fitted, awaterproof seal is inserted.
 34. The method of claim 31, wherein uponmounting a drum guide for sealing, the drum guide is mounted inside themain drum prior to inserting the sub drum into the main drum.
 35. Themethod of claim 31, wherein in the coupling of the shaft-spider assemblyto the rear of the main drum, the end of the main drum spider is coupledto the main drum.